Programs & Examples On #Health monitoring

Health monitoring gives an easy way to monitor the overall health of an application and the underlying systems

SQL Server reports 'Invalid column name', but the column is present and the query works through management studio

I suspect that you have two tables with the same name. One is owned by the schema 'dbo' (dbo.PerfDiag), and the other is owned by the default schema of the account used to connect to SQL Server (something like userid.PerfDiag).

When you have an unqualified reference to a schema object (such as a table) — one not qualified by schema name — the object reference must be resolved. Name resolution occurs by searching in the following sequence for an object of the appropriate type (table) with the specified name. The name resolves to the first match:

  • Under the default schema of the user.
  • Under the schema 'dbo'.

The unqualified reference is bound to the first match in the above sequence.

As a general recommended practice, one should always qualify references to schema objects, for performance reasons:

  • An unqualified reference may invalidate a cached execution plan for the stored procedure or query, since the schema to which the reference was bound may change depending on the credentials executing the stored procedure or query. This results in recompilation of the query/stored procedure, a performance hit. Recompilations cause compile locks to be taken out, blocking others from accessing the needed resource(s).

  • Name resolution slows down query execution as two probes must be made to resolve to the likely version of the object (that owned by 'dbo'). This is the usual case. The only time a single probe will resolve the name is if the current user owns an object of the specified name and type.

[Edited to further note]

The other possibilities are (in no particular order):

  • You aren't connected to the database you think you are.
  • You aren't connected to the SQL Server instance you think you are.

Double check your connect strings and ensure that they explicitly specify the SQL Server instance name and the database name.

Xcode 12, building for iOS Simulator, but linking in object file built for iOS, for architecture arm64

On Build Settings search VALID_ARCH then press delete. This should work for me with Xcode 12.0.1

VALID_ARCH on build settings

How to check all versions of python installed on osx and centos

COMMAND: python --version && python3 --version

OUTPUT:

Python 2.7.10
Python 3.7.1

ALIAS COMMAND: pyver

OUTPUT:

Python 2.7.10
Python 3.7.1

You can make an alias like "pyver" in your .bashrc file or else using a text accelerator like AText maybe.

Pandas create empty DataFrame with only column names

Creating colnames with iterating

df = pd.DataFrame(columns=['colname_' + str(i) for i in range(5)])
print(df)

# Empty DataFrame
# Columns: [colname_0, colname_1, colname_2, colname_3, colname_4]
# Index: []

to_html() operations

print(df.to_html())

# <table border="1" class="dataframe">
#   <thead>
#     <tr style="text-align: right;">
#       <th></th>
#       <th>colname_0</th>
#       <th>colname_1</th>
#       <th>colname_2</th>
#       <th>colname_3</th>
#       <th>colname_4</th>
#     </tr>
#   </thead>
#   <tbody>
#   </tbody>
# </table>

this seems working

print(type(df.to_html()))
# <class 'str'>

The problem is caused by

when you create df like this

df = pd.DataFrame(columns=COLUMN_NAMES)

it has 0 rows × n columns, you need to create at least one row index by

df = pd.DataFrame(columns=COLUMN_NAMES, index=[0])

now it has 1 rows × n columns. You are be able to add data. Otherwise its df that only consist colnames object(like a string list).

how to make a html iframe 100% width and height?

this code probable help you .

<iframe src="" onload="this.width=screen.width;this.height=screen.height;">

How to show x and y axes in a MATLAB graph?

Inspired by @Luisa's answer, I made a function, axes0

x = linspace(-2,2,101);
plot(x,2*x.^3-3*x+1);
axes0

Example output for axes0

You can follow the link above to download the function and get more details on usage

Sending HTTP POST with System.Net.WebClient

Based on @carlosfigueira 's answer, I looked further into WebClient's methods and found UploadValues, which is exactly what I want:

Using client As New Net.WebClient
    Dim reqparm As New Specialized.NameValueCollection
    reqparm.Add("param1", "somevalue")
    reqparm.Add("param2", "othervalue")
    Dim responsebytes = client.UploadValues(someurl, "POST", reqparm)
    Dim responsebody = (New Text.UTF8Encoding).GetString(responsebytes)
End Using

The key part is this:

client.UploadValues(someurl, "POST", reqparm)

It sends whatever verb I type in, and it also helps me create a properly url encoded form data, I just have to supply the parameters as a namevaluecollection.

Media Queries: How to target desktop, tablet, and mobile?

  1. I have used this site to find the resolution and developed CSS per actual numbers. My numbers vary quite a bit from the above answers, except that the my CSS actually hits the desired devices.

  2. Also, have this debugging piece of code right after your media query e.g:

    @media only screen and (min-width: 769px) and (max-width: 1281px) { 
      /* for 10 inches tablet screens */
      body::before {
        content: "tablet to some desktop media query (769 > 1281) fired";
        font-weight: bold;
        display: block;
        text-align: center;
        background: rgba(255, 255, 0, 0.9); /* Semi-transparent yellow */
        position: absolute;
        top: 0;
        left: 0;
        right: 0;
        z-index: 99;
      }
    } 
    

    Add this debugging item in every single media query and you will see what query has being applied.

Python calling method in class

The first argument of all methods is usually called self. It refers to the instance for which the method is being called.

Let's say you have:

class A(object):
    def foo(self):
        print 'Foo'

    def bar(self, an_argument):
        print 'Bar', an_argument

Then, doing:

a = A()
a.foo() #prints 'Foo'
a.bar('Arg!') #prints 'Bar Arg!'

There's nothing special about this being called self, you could do the following:

class B(object):
    def foo(self):
        print 'Foo'

    def bar(this_object):
        this_object.foo()

Then, doing:

b = B()
b.bar() # prints 'Foo'

In your specific case:

dangerous_device = MissileDevice(some_battery)
dangerous_device.move(dangerous_device.RIGHT) 

(As suggested in comments MissileDevice.RIGHT could be more appropriate here!)

You could declare all your constants at module level though, so you could do:

dangerous_device.move(RIGHT)

This, however, is going to depend on how you want your code to be organized!

How can I determine if a .NET assembly was built for x86 or x64?

Below is a batch file that will run corflags.exe against all dlls and exes in the current working directory and all sub-directories, parse the results and display the target architecture of each.

Depending on the version of corflags.exe that is used, the line items in the output will either include 32BIT, or 32BITREQ (and 32BITPREF). Whichever of these two is included in the output is the critical line item that must be checked to differentiate between Any CPU and x86. If you are using an older version of corflags.exe (pre Windows SDK v8.0A), then only the 32BIT line item will be present in the output, as others have indicated in past answers. Otherwise 32BITREQ and 32BITPREF replace it.

This assumes corflags.exe is in the %PATH%. The simplest way to ensure this is to use a Developer Command Prompt. Alternatively you could copy it from it's default location.

If the batch file below is run against an unmanaged dll or exe, it will incorrectly display it as x86, since the actual output from Corflags.exe will be an error message similar to:

corflags : error CF008 : The specified file does not have a valid managed header

@echo off

echo.
echo Target architecture for all exes and dlls:
echo.

REM For each exe and dll in this directory and all subdirectories...
for %%a in (.exe, .dll) do forfiles /s /m *%%a /c "cmd /c echo @relpath" > testfiles.txt

for /f %%b in (testfiles.txt) do (
    REM Dump corflags results to a text file
    corflags /nologo %%b > corflagsdeets.txt

   REM Parse the corflags results to look for key markers   
   findstr /C:"PE32+">nul .\corflagsdeets.txt && (      
      REM `PE32+` indicates x64
        echo %%~b = x64
    ) || (
      REM pre-v8 Windows SDK listed only "32BIT" line item, 
      REM newer versions list "32BITREQ" and "32BITPREF" line items
        findstr /C:"32BITREQ  : 0">nul /C:"32BIT     : 0" .\corflagsdeets.txt && (
            REM `PE32` and NOT 32bit required indicates Any CPU
            echo %%~b = Any CPU
        ) || (
            REM `PE32` and 32bit required indicates x86
            echo %%~b = x86
        )
    )

    del corflagsdeets.txt
)

del testfiles.txt
echo.

Case-insensitive search in Rails model

Find_or_create is now deprecated, you should use an AR Relation instead plus first_or_create, like so:

TombolaEntry.where("lower(name) = ?", self.name.downcase).first_or_create(name: self.name)

This will return the first matched object, or create one for you if none exists.

How do I remove the passphrase for the SSH key without having to create a new key?

In windows for me it kept saying "id_ed25135: No such file or directory" upon entering above commands. So I went to the folder, copied the path within folder explorer and added "\id_ed25135" at the end.

This is what I ended up typing and worked:
ssh-keygen -p -f C:\Users\john\.ssh\id_ed25135

This worked. Because for some reason, in Cmder the default path was something like this C:\Users\capit/.ssh/id_ed25135 (some were backslashes: "\" and some were forward slashes: "/")

The localhost page isn’t working localhost is currently unable to handle this request. HTTP ERROR 500

Here's an answer to a 2-year old question in case it helps anyone else with the same problem.

Based upon the information you've provided, a permissions issue on the file (or files) would be one cause of the same 500 Internal Server Error.

To check whether this is the problem (if you can't get more detailed information on the error), navigate to the directory in Terminal and run the following command:

ls -la

If you see limited permissions - e.g. -rw-------@ against your file, then that's your problem.

The solution then is to run chmod 644 on the problem file(s) or chmod 755 on the directories. See this answer - How do I set chmod for a folder and all of its subfolders and files? - for a detailed explanation of how to change permissions.

By way of background, I had precisely the same problem as you did on some files that I had copied over from another Mac via Google Drive, which transfer had stripped most of the permissions from the files.

The screenshot below illustrates. The index.php file with the -rw-------@ permissions generates a 500 Internal Server Error, while the index_finstuff.php (precisely the same content!) with -rw-r--r--@ permissions is fine. Changing the permissions on the index.php immediately resolves the problem.

In other words, your PHP code and the server may both be fine. However, the limited read permissions on the file may be forbidding the server from displaying the content, causing the 500 Internal Server Error message to be displayed instead.

enter image description here

What are the differences between json and simplejson Python modules?

The builtin json module got included in Python 2.6. Any projects that support versions of Python < 2.6 need to have a fallback. In many cases, that fallback is simplejson.

AppFabric installation failed because installer MSI returned with error code : 1603

My problem was that there was task already for Customer Experience Improvement Program in Task Scheduler "\Microsoft\Windows\AppFabric\Customer Experience Improvement Program\Consolidator". I removed that task and after that installation succeeded.

How can I analyze a heap dump in IntelliJ? (memory leak)

You can install the JVisualVM plugin from here: https://plugins.jetbrains.com/plugin/3749?pr=

This will allow you to analyse the dump within the plugin.

Pass array to mvc Action via AJAX

If you're using ASP.NET Core MVC and need to handle the square brackets (rather than use the jQuery "traditional" option), the only option I've found is to manually build the IEnumerable in the contoller method.

string arrayKey = "p[]=";
var pArray = HttpContext.Request.QueryString.Value
    .Split('&')
    .Where(s => s.Contains(arrayKey))
    .Select(s => s.Substring(arrayKey.Length));

Uncaught SyntaxError: Invalid or unexpected token

You should pass @item.email in quotes then it will be treated as string argument

<td><a href ="#"  onclick="Getinfo('@item.email');" >6/16/2016 2:02:29 AM</a>  </td>

Otherwise, it is treated as variable thus error is generated.

What causes and what are the differences between NoClassDefFoundError and ClassNotFoundException?

The difference from the Java API Specifications is as follows.

For ClassNotFoundException:

Thrown when an application tries to load in a class through its string name using:

  • The forName method in class Class.
  • The findSystemClass method in class ClassLoader.
  • The loadClass method in class ClassLoader.

but no definition for the class with the specified name could be found.

For NoClassDefFoundError:

Thrown if the Java Virtual Machine or a ClassLoader instance tries to load in the definition of a class (as part of a normal method call or as part of creating a new instance using the new expression) and no definition of the class could be found.

The searched-for class definition existed when the currently executing class was compiled, but the definition can no longer be found.

So, it appears that the NoClassDefFoundError occurs when the source was successfully compiled, but at runtime, the required class files were not found. This may be something that can happen in the distribution or production of JAR files, where not all the required class files were included.

As for ClassNotFoundException, it appears that it may stem from trying to make reflective calls to classes at runtime, but the classes the program is trying to call is does not exist.

The difference between the two is that one is an Error and the other is an Exception. With NoClassDefFoundError is an Error and it arises from the Java Virtual Machine having problems finding a class it expected to find. A program that was expected to work at compile-time can't run because of class files not being found, or is not the same as was produced or encountered at compile-time. This is a pretty critical error, as the program cannot be initiated by the JVM.

On the other hand, the ClassNotFoundException is an Exception, so it is somewhat expected, and is something that is recoverable. Using reflection is can be error-prone (as there is some expectations that things may not go as expected. There is no compile-time check to see that all the required classes exist, so any problems with finding the desired classes will appear at runtime.

CRC32 C or C++ implementation

pycrc is a Python script that generates C CRC code, with options to select the CRC size, algorithm and model.

It's released under the MIT licence. Is that acceptable for your purposes?

Is there a way to pass jvm args via command line to maven?

I think MAVEN_OPTS would be most appropriate for you. See here: http://maven.apache.org/configure.html

In Unix:

Add the MAVEN_OPTS environment variable to specify JVM properties, e.g. export MAVEN_OPTS="-Xms256m -Xmx512m". This environment variable can be used to supply extra options to Maven.

In Win, you need to set environment variable via the dialogue box

Add ... environment variable by opening up the system properties (WinKey + Pause),... In the same dialog, add the MAVEN_OPTS environment variable in the user variables to specify JVM properties, e.g. the value -Xms256m -Xmx512m. This environment variable can be used to supply extra options to Maven.

Force hide address bar in Chrome on Android

window.scrollTo(0,1);

this will help you but this javascript is may not work in all browsers

Using DataContractSerializer to serialize, but can't deserialize back

Other solution is:

public static T Deserialize<T>(string rawXml)
{
    using (XmlReader reader = XmlReader.Create(new StringReader(rawXml)))
    {
        DataContractSerializer formatter0 = 
            new DataContractSerializer(typeof(T));
        return (T)formatter0.ReadObject(reader);
    }
}

One remark: sometimes it happens that raw xml contains e.g.:

<?xml version="1.0" encoding="utf-16"?>

then of course you can't use UTF8 encoding used in other examples..

VBA test if cell is in a range

If the two ranges to be tested (your given cell and your given range) are not in the same Worksheet, then Application.Intersect throws an error. Thus, a way to avoid it is with something like

Sub test_inters(rng1 As Range, rng2 As Range)
    If (rng1.Parent.Name = rng2.Parent.Name) Then
        Dim ints As Range
        Set ints = Application.Intersect(rng1, rng2)
        If (Not (ints Is Nothing)) Then
            ' Do your job
        End If
    End If
End Sub

How to allow only integers in a textbox?

Just use

<input type="number" id="foo" runat="server" />

It'll work on all modern browsers except IE +10. Here is a full list:

http://caniuse.com/#feat=input-number

Redirect to specified URL on PHP script completion?

Here's a solution to the "headers were already sent" problem. Assume you are validating and emailing a form. Make sure the php code is the first thing on your page... before any of the doctype and head tags and all that jazz. Then, when the POST arrives back at the page the php code will come first and not encounter the headers already sent problem.

Error in Process.Start() -- The system cannot find the file specified

You can use the folowing to get the full path to your program like this:

Environment.CurrentDirectory

JFrame Maximize window

If you're using a JFrame, try this

JFrame frame = new JFrame();
//...
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);

The difference between fork(), vfork(), exec() and clone()

The fork(),vfork() and clone() all call the do_fork() to do the real work, but with different parameters.

asmlinkage int sys_fork(struct pt_regs regs)
{
    return do_fork(SIGCHLD, regs.esp, &regs, 0);
}

asmlinkage int sys_clone(struct pt_regs regs)
{
    unsigned long clone_flags;
    unsigned long newsp;

    clone_flags = regs.ebx;
    newsp = regs.ecx;
    if (!newsp)
        newsp = regs.esp;
    return do_fork(clone_flags, newsp, &regs, 0);
}
asmlinkage int sys_vfork(struct pt_regs regs)
{
    return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.esp, &regs, 0);
}
#define CLONE_VFORK 0x00004000  /* set if the parent wants the child to wake it up on mm_release */
#define CLONE_VM    0x00000100  /* set if VM shared between processes */

SIGCHLD means the child should send this signal to its father when exit.

For fork, the child and father has the independent VM page table, but since the efficiency, fork will not really copy any pages, it just set all the writeable pages to readonly for child process. So when child process want to write something on that page, an page exception happen and kernel will alloc a new page cloned from the old page with write permission. That's called "copy on write".

For vfork, the virtual memory is exactly by child and father---just because of that, father and child can't be awake concurrently since they will influence each other. So the father will sleep at the end of "do_fork()" and awake when child call exit() or execve() since then it will own new page table. Here is the code(in do_fork()) that the father sleep.

if ((clone_flags & CLONE_VFORK) && (retval > 0))
down(&sem);
return retval;

Here is the code(in mm_release() called by exit() and execve()) which awake the father.

up(tsk->p_opptr->vfork_sem);

For sys_clone(), it is more flexible since you can input any clone_flags to it. So pthread_create() call this system call with many clone_flags:

int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL | CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM);

Summary: the fork(),vfork() and clone() will create child processes with different mount of sharing resource with the father process. We also can say the vfork() and clone() can create threads(actually they are processes since they have independent task_struct) since they share the VM page table with father process.

How to import a Python class that is in a directory above?

Import module from a directory which is exactly one level above the current directory:

from .. import module

Calling an API from SQL Server stored procedure

I'd recommend using a CLR user defined function, if you already know how to program in C#, then the code would be;

using System.Data.SqlTypes;
using System.Net;

public partial class UserDefinedFunctions
{
 [Microsoft.SqlServer.Server.SqlFunction]
 public static SqlString http(SqlString url)
 {
  var wc = new WebClient();
  var html = wc.DownloadString(url.Value);
  return new SqlString (html);
 }
}

And here's installation instructions; https://blog.dotnetframework.org/2019/09/17/make-a-http-request-from-sqlserver-using-a-clr-udf/

Adding items to end of linked list

You want to navigate through the entire linked list using a loop and checking the "next" value for each node. The last node will be the one whose next value is null. Simply make this node's next value a new node which you create with the input data.

node temp = first; // starts with the first node.

    while (temp.next != null)
    {
       temp = temp.next;
    }

temp.next = new Node(header, x);

That's the basic idea. This is of course, pseudo code, but it should be simple enough to implement.

How to enable MySQL Query Log?

I use this method for logging when I want to quickly optimize different page loads. It's a little tip...

Logging to a TABLE

SET global general_log = 1;
SET global log_output = 'table';

You can then select from my mysql.general_log table to retrieve recent queries.

I can then do something similar to tail -f on the mysql.log, but with more refinements...

select * from mysql.general_log 
where  event_time  > (now() - INTERVAL 8 SECOND) and thread_id not in(9 , 628)
and argument <> "SELECT 1" and argument <> "" 
and argument <> "SET NAMES 'UTF8'"  and argument <> "SHOW STATUS"  
and command_type = "Query"  and argument <> "SET PROFILING=1"

This makes it easy to see my queries that I can try and cut back. I use 8 seconds interval to only fetch queries executed within the last 8 seconds.

What is an ORM, how does it work, and how should I use one?

Introduction

Object-Relational Mapping (ORM) is a technique that lets you query and manipulate data from a database using an object-oriented paradigm. When talking about ORM, most people are referring to a library that implements the Object-Relational Mapping technique, hence the phrase "an ORM".

An ORM library is a completely ordinary library written in your language of choice that encapsulates the code needed to manipulate the data, so you don't use SQL anymore; you interact directly with an object in the same language you're using.

For example, here is a completely imaginary case with a pseudo language:

You have a book class, you want to retrieve all the books of which the author is "Linus". Manually, you would do something like that:

book_list = new List();
sql = "SELECT book FROM library WHERE author = 'Linus'";
data = query(sql); // I over simplify ...
while (row = data.next())
{
     book = new Book();
     book.setAuthor(row.get('author');
     book_list.add(book);
}

With an ORM library, it would look like this:

book_list = BookTable.query(author="Linus");

The mechanical part is taken care of automatically via the ORM library.

Pros and Cons

Using ORM saves a lot of time because:

  • DRY: You write your data model in only one place, and it's easier to update, maintain, and reuse the code.
  • A lot of stuff is done automatically, from database handling to I18N.
  • It forces you to write MVC code, which, in the end, makes your code a little cleaner.
  • You don't have to write poorly-formed SQL (most Web programmers really suck at it, because SQL is treated like a "sub" language, when in reality it's a very powerful and complex one).
  • Sanitizing; using prepared statements or transactions are as easy as calling a method.

Using an ORM library is more flexible because:

  • It fits in your natural way of coding (it's your language!).
  • It abstracts the DB system, so you can change it whenever you want.
  • The model is weakly bound to the rest of the application, so you can change it or use it anywhere else.
  • It lets you use OOP goodness like data inheritance without a headache.

But ORM can be a pain:

  • You have to learn it, and ORM libraries are not lightweight tools;
  • You have to set it up. Same problem.
  • Performance is OK for usual queries, but a SQL master will always do better with his own SQL for big projects.
  • It abstracts the DB. While it's OK if you know what's happening behind the scene, it's a trap for new programmers that can write very greedy statements, like a heavy hit in a for loop.

How to learn about ORM?

Well, use one. Whichever ORM library you choose, they all use the same principles. There are a lot of ORM libraries around here:

If you want to try an ORM library in Web programming, you'd be better off using an entire framework stack like:

  • Symfony (PHP, using Propel or Doctrine).
  • Django (Python, using a internal ORM).

Do not try to write your own ORM, unless you are trying to learn something. This is a gigantic piece of work, and the old ones took a lot of time and work before they became reliable.

How to add a filter class in Spring Boot?

Here is an example of my custom Filter class:

package com.dawson.controller.filter;

import org.springframework.stereotype.Component;
import org.springframework.web.filter.GenericFilterBean;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


@Component
public class DawsonApiFilter extends GenericFilterBean {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        if (req.getHeader("x-dawson-nonce") == null || req.getHeader("x-dawson-signature") == null) {
            HttpServletResponse httpResponse = (HttpServletResponse) response;
            httpResponse.setContentType("application/json");
            httpResponse.sendError(HttpServletResponse.SC_BAD_REQUEST, "Required headers not specified in the request");
            return;
        }
        chain.doFilter(request, response);
    }
}

And I added it to the Spring boot configuration by adding it to Configuration class as follows:

package com.dawson.configuration;

import com.fasterxml.jackson.datatype.hibernate5.Hibernate5Module;
import com.dawson.controller.filter.DawsonApiFilter;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

@SpringBootApplication
public class ApplicationConfiguration {
    @Bean
    public FilterRegistrationBean dawsonApiFilter() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new DawsonApiFilter());
// In case you want the filter to apply to specific URL patterns only
        registration.addUrlPatterns("/dawson/*");
        return registration;
    }
}

How to disable/enable select field using jQuery?

Disabled is a Boolean Attribute of the select element as stated by WHATWG, that means the RIGHT WAY TO DISABLE with jQuery would be

jQuery("#selectId").attr('disabled',true);

This would make this HTML

<select id="selectId" name="gender" disabled="disabled">
    <option value="-1">--Select a Gender--</option>
    <option value="0">Male</option>
    <option value="1">Female</option>
</select>

This works for both XHTML and HTML (W3School reference)

Yet it also can be done using it as property

jQuery("#selectId").prop('disabled', 'disabled');

getting

<select id="selectId" name="gender" disabled>

Which only works for HTML and not XTML

NOTE: A disabled element will not be submitted with the form as answered in this question: The disabled form element is not submitted

NOTE2: A disabled element may be greyed out.

NOTE3:

A form control that is disabled must prevent any click events that are queued on the user interaction task source from being dispatched on the element.

TL;DR

<script>
    var update_pizza = function () {
        if ($("#pizza").is(":checked")) {
            $('#pizza_kind').attr('disabled', false);
        } else {
            $('#pizza_kind').attr('disabled', true);
        }
    };
    $(update_pizza);
    $("#pizza").change(update_pizza);
</script>

Get index of a key in json

What you are after are numerical indexes in the way classic arrays work, however there is no such thing with json object/associative arrays.

"key1", "key2" themeselves are the indexes and there is no numerical index associated with them. If you want to have such functionality you have to assiciate them yourself.

Authenticating against Active Directory with Java on Linux

If all you want to do is authenticate against AD using Kerberos, then a simple http://spnego.sourceforge.net/HelloKDC.java program should do it.

Take a look at the project's "pre-flight" documentation which talks about the HelloKDC.java program.

ArrayList filter

As you didn't give us very much information, I'm assuming the language you're writing the code in is C#. First of all: Prefer System.Collections.Generic.List over an ArrayList. Secondly: One way would be to loop through every item in the list and check whether it contains "How". Another way would be to use LINQ. Here's a quick example that filters out every item which doesn't contain "How":

var list = new List<string>();
list.AddRange(new string[] {
    "How are you?",
    "How you doing?",
    "Joe",
    "Mike", });

foreach (string str in list.Where(s => s.Contains("How")))
{
    Console.WriteLine(str);
}
Console.ReadLine();

How can I merge properties of two JavaScript objects dynamically?

I use the following which is in pure JavaScript. It starts from the right-most argument and combines them all the way up to the first argument. There is no return value, only the first argument is modified and the left-most parameter (except the first one) has the highest weight on properties.

var merge = function() {
  var il = arguments.length;

  for (var i = il - 1; i > 0; --i) {
    for (var key in arguments[i]) {
      if (arguments[i].hasOwnProperty(key)) {
        arguments[0][key] = arguments[i][key];
      }
    }
  }
};

ASP.NET Core form POST results in a HTTP 415 Unsupported Media Type response

First you need to specify in the Headers the Content-Type, for example, it can be application/json.

If you set application/json content type, then you need to send a json.

So in the body of your request you will send not form-data, not x-www-for-urlencoded but a raw json, for example {"Username": "user", "Password": "pass"}

You can adapt the example to various content types, including what you want to send.

You can use a tool like Postman or curl to play with this.

What is the most efficient way to check if a value exists in a NumPy array?

Adding to @HYRY's answer in1d seems to be fastest for numpy. This is using numpy 1.8 and python 2.7.6.

In this test in1d was fastest, however 10 in a look cleaner:

a = arange(0,99999,3)
%timeit 10 in a
%timeit in1d(a, 10)

10000 loops, best of 3: 150 µs per loop
10000 loops, best of 3: 61.9 µs per loop

Constructing a set is slower than calling in1d, but checking if the value exists is a bit faster:

s = set(range(0, 99999, 3))
%timeit 10 in s

10000000 loops, best of 3: 47 ns per loop

How to read integer values from text file

How large are the values? Java 6 has Scanner class that can read anything from int (32 bit), long (64-bit) to BigInteger (arbitrary big integer).

For Java 5 or 4, Scanner is there, but no support for BigInteger. You have to read line by line (with readLine of Scanner class) and create BigInteger object from the String.

Search and get a line in Python

items=re.findall("token.*$",s,re.MULTILINE)
>>> for x in items:

you can also get the line if there are other characters before token

items=re.findall("^.*token.*$",s,re.MULTILINE)

The above works like grep token on unix and keyword 'in' or .contains in python and C#

s='''
qwertyuiop
asdfghjkl

zxcvbnm
token qwerty

asdfghjklñ
'''

http://pythex.org/ matches the following 2 lines

....
....
token qwerty

The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path

I came across the same issue. I tried adding the server in "Server Runtime" but unfortunately that didn't work for me.

What worked for me is, I added javax.servlet-api-3.0.1.jar file in build path. On the other hand If It's a Maven project add dependency for this jar file. This would definitely work.

How do I ZIP a file in C#, using no 3rd-party APIs?

How can I programatically (C#) ZIP a file (in Windows) without using any third party libraries?

If using the 4.5+ Framework, there is now the ZipArchive and ZipFile classes.

using (ZipArchive zip = ZipFile.Open("test.zip", ZipArchiveMode.Create))
{
    zip.CreateEntryFromFile(@"c:\something.txt", "data/path/something.txt");
}

You need to add references to:

  • System.IO.Compression
  • System.IO.Compression.FileSystem

For .NET Core targeting net46, you need to add dependencies for

  • System.IO.Compression
  • System.IO.Compression.ZipFile

Example project.json:

"dependencies": {
  "System.IO.Compression": "4.1.0",
  "System.IO.Compression.ZipFile": "4.0.1"
},

"frameworks": {
  "net46": {}
}

For .NET Core 2.0, just adding a simple using statement is all that is needed:

  • using System.IO.Compression;

PostgreSQL database default location on Linux

/var/lib/postgresql/[version]/data/

At least in Gentoo Linux and Ubuntu 14.04 by default.

You can find postgresql.conf and look at param data_directory. If it is commented then database directory is the same as this config file directory.

Error: " 'dict' object has no attribute 'iteritems' "

In Python2, we had .items() and .iteritems() in dictionaries. dict.items() returned list of tuples in dictionary [(k1,v1),(k2,v2),...]. It copied all tuples in dictionary and created new list. If dictionary is very big, there is very big memory impact.

So they created dict.iteritems() in later versions of Python2. This returned iterator object. Whole dictionary was not copied so there is lesser memory consumption. People using Python2 are taught to use dict.iteritems() instead of .items() for efficiency as explained in following code.

import timeit

d = {i:i*2 for i in xrange(10000000)}  
start = timeit.default_timer()
for key,value in d.items():
    tmp = key + value #do something like print
t1 = timeit.default_timer() - start

start = timeit.default_timer()
for key,value in d.iteritems():
    tmp = key + value
t2 = timeit.default_timer() - start

Output:

Time with d.items(): 9.04773592949
Time with d.iteritems(): 2.17707300186

In Python3, they wanted to make it more efficient, so moved dictionary.iteritems() to dict.items(), and removed .iteritems() as it was no longer needed.

You have used dict.iteritems() in Python3 so it has failed. Try using dict.items() which has the same functionality as dict.iteritems() of Python2. This is a tiny bit migration issue from Python2 to Python3.

Can I have multiple background images using CSS?

Yes, it is possible, and has been implemented by popular usability testing website Silverback. If you look through the source code you can see that the background is made up of several images, placed on top of each other.

Here is the article demonstrating how to do the effect can be found on Vitamin. A similar concept for wrapping these 'onion skin' layers can be found on A List Apart.

What is the purpose of the : (colon) GNU Bash builtin?

If you'd like to truncate a file to zero bytes, useful for clearing logs, try this:

:> file.log

Give column name when read csv file pandas

user1  = pd.read_csv('dataset/1.csv',  names=['Time',  'X',  'Y',  'Z']) 

names parameter in read_csv function is used to define column names. If you pass extra name in this list, it will add another new column with that name with NaN values.

header=None is used to trim column names is already exists in CSV file.

XMLHttpRequest cannot load an URL with jQuery

I am using WebAPI 3 and was facing the same issue. The issue has resolve as @Rytis added his solution. And I think in WebAPI 3, we don't need to define method RegisterWebApi.

My change was only in web.config file and is working.

<httpProtocol>
 <customHeaders>
 <add name="Access-Control-Allow-Origin" value="*" />
 <add name="Access-Control-Allow-Methods" value="GET, POST" />
</customHeaders>
</httpProtocol> 

Thanks for you solution @Rytis!

How to display a database table on to the table in the JSP page

Tracking ID Track
    <br>
    <%String id = request.getParameter("track_id");%>
       <%if (id.length() == 0) {%>
    <b><h1>Please Enter Tracking ID</h1></b>
    <% } else {%>
    <div class="container">
        <table border="1" class="table" >
            <thead>
                <tr class="warning" >
                    <td ><h4>Track ID</h4></td>
                    <td><h4>Source</h4></td>
                    <td><h4>Destination</h4></td>
                    <td><h4>Current Status</h4></td>

                </tr>
            </thead>
            <%
                try {
                    connection = DriverManager.getConnection(connectionUrl + database, userid, password);
                    statement = connection.createStatement();
                    String sql = "select * from track where track_id="+ id;
                    resultSet = statement.executeQuery(sql);
                    while (resultSet.next()) {
            %>
            <tr class="info">
                <td><%=resultSet.getString("track_id")%></td>
                <td><%=resultSet.getString("source")%></td>
                <td><%=resultSet.getString("destination")%></td>
                <td><%=resultSet.getString("status")%></td>
            </tr>
            <%
                    }
                    connection.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            %>
        </table>

        <%}%>
</body>

How to extract the decision rules from scikit-learn decision-tree?

This is the code you need

I have modified the top liked code to indent in a jupyter notebook python 3 correctly

import numpy as np
from sklearn.tree import _tree

def tree_to_code(tree, feature_names):
    tree_ = tree.tree_
    feature_name = [feature_names[i] 
                    if i != _tree.TREE_UNDEFINED else "undefined!" 
                    for i in tree_.feature]
    print("def tree({}):".format(", ".join(feature_names)))

    def recurse(node, depth):
        indent = "    " * depth
        if tree_.feature[node] != _tree.TREE_UNDEFINED:
            name = feature_name[node]
            threshold = tree_.threshold[node]
            print("{}if {} <= {}:".format(indent, name, threshold))
            recurse(tree_.children_left[node], depth + 1)
            print("{}else:  # if {} > {}".format(indent, name, threshold))
            recurse(tree_.children_right[node], depth + 1)
        else:
            print("{}return {}".format(indent, np.argmax(tree_.value[node])))

    recurse(0, 1)

How to check whether a Storage item is set?

easist way is

if(localStorage.test){
console.log("now defined");
}
else{
console.log("undefined");
localStorage.test="defined;"
}

How it works

when you call localStorage.test first time it does not contain any store into localStorage object so it returns undefined else condition triggers. after else triggered i set new variable and again check it contains data so it return data with true in if condition

Python: create dictionary using dict() with integer keys?

a = dict(one=1, two=2, three=3)

Providing keyword arguments as in this example only works for keys that are valid Python identifiers. Otherwise, any valid keys can be used.

java IO Exception: Stream Closed

You're calling writer.close(); after you've done writing to it. Once a stream is closed, it can not be written to again. Usually, the way I go about implementing this is by moving the close out of the write to method.

public void writeToFile(){
    String file_text= pedStatusText + "     " + gatesStatus + "     " + DrawBridgeStatusText;
    try {
        writer.write(file_text);
        writer.flush();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

And add a method cleanUp to close the stream.

public void cleanUp() {
     writer.close();
}

This means that you have the responsibility to make sure that you're calling cleanUp when you're done writing to the file. Failure to do this will result in memory leaks and resource locking.

EDIT: You can create a new stream each time you want to write to the file, by moving writer into the writeToFile() method..

 public void writeToFile() {
    FileWriter writer = new FileWriter("status.txt", true);
    // ... Write to the file.

    writer.close();
 }

How do you properly use namespaces in C++?

I did not see any mention of it in the other answers, so here are my 2 Canadian cents:

On the "using namespace" topic, a useful statement is the namespace alias, allowing you to "rename" a namespace, normally to give it a shorter name. For example, instead of:

Some::Impossibly::Annoyingly::Long:Name::For::Namespace::Finally::TheClassName foo;
Some::Impossibly::Annoyingly::Long:Name::For::Namespace::Finally::AnotherClassName bar;

you can write:

namespace Shorter = Some::Impossibly::Annoyingly::Long:Name::For::Namespace::Finally;
Shorter::TheClassName foo;
Shorter::AnotherClassName bar;

Capturing a single image from my webcam in Java or Python

Some time ago I wrote simple Webcam Capture API which can be used for that. The project is available on Github.

Example code:

Webcam webcam = Webcam.getDefault();
webcam.open();
try {
  ImageIO.write(webcam.getImage(), "PNG", new File("test.png"));
} catch (IOException e) {
  e.printStackTrace();
} finally {
  webcam.close();
}

MySQL - How to select data by string length

select * from *tablename* where 1 having length(*fieldname*)=*fieldlength*

Example if you want to select from customer the entry's with a name shorter then 2 chars.

select * from customer where 1 **having length(name)<2**

How to encrypt and decrypt file in Android?

Use a CipherOutputStream or CipherInputStream with a Cipher and your FileInputStream / FileOutputStream.

I would suggest something like Cipher.getInstance("AES/CBC/PKCS5Padding") for creating the Cipher class. CBC mode is secure and does not have the vulnerabilities of ECB mode for non-random plaintexts. It should be present in any generic cryptographic library, ensuring high compatibility.

Don't forget to use a Initialization Vector (IV) generated by a secure random generator if you want to encrypt multiple files with the same key. You can prefix the plain IV at the start of the ciphertext. It is always exactly one block (16 bytes) in size.

If you want to use a password, please make sure you do use a good key derivation mechanism (look up password based encryption or password based key derivation). PBKDF2 is the most commonly used Password Based Key Derivation scheme and it is present in most Java runtimes, including Android. Note that SHA-1 is a bit outdated hash function, but it should be fine in PBKDF2, and does currently present the most compatible option.

Always specify the character encoding when encoding/decoding strings, or you'll be in trouble when the platform encoding differs from the previous one. In other words, don't use String.getBytes() but use String.getBytes(StandardCharsets.UTF_8).

To make it more secure, please add cryptographic integrity and authenticity by adding a secure checksum (MAC or HMAC) over the ciphertext and IV, preferably using a different key. Without an authentication tag the ciphertext may be changed in such a way that the change cannot be detected.

Be warned that CipherInputStream may not report BadPaddingException, this includes BadPaddingException generated for authenticated ciphers such as GCM. This would make the streams incompatible and insecure for these kind of authenticated ciphers.

Google Spreadsheet, Count IF contains a string

It will likely have been solved by now, but I ran accross this and figured to give my input

=COUNTIF(a2:a51;"*iPad*")

The important thing is that separating parameters in google docs is using a ; and not a ,

Gradle: How to Display Test Results in the Console in Real Time?

Here is my fancy version:

fancy test result

import org.gradle.api.tasks.testing.logging.TestExceptionFormat
import org.gradle.api.tasks.testing.logging.TestLogEvent

tasks.withType(Test) {
    testLogging {
        // set options for log level LIFECYCLE
        events TestLogEvent.FAILED,
               TestLogEvent.PASSED,
               TestLogEvent.SKIPPED,
               TestLogEvent.STANDARD_OUT
        exceptionFormat TestExceptionFormat.FULL
        showExceptions true
        showCauses true
        showStackTraces true

        // set options for log level DEBUG and INFO
        debug {
            events TestLogEvent.STARTED,
                   TestLogEvent.FAILED,
                   TestLogEvent.PASSED,
                   TestLogEvent.SKIPPED,
                   TestLogEvent.STANDARD_ERROR,
                   TestLogEvent.STANDARD_OUT
            exceptionFormat TestExceptionFormat.FULL
        }
        info.events = debug.events
        info.exceptionFormat = debug.exceptionFormat

        afterSuite { desc, result ->
            if (!desc.parent) { // will match the outermost suite
                def output = "Results: ${result.resultType} (${result.testCount} tests, ${result.successfulTestCount} passed, ${result.failedTestCount} failed, ${result.skippedTestCount} skipped)"
                def startItem = '|  ', endItem = '  |'
                def repeatLength = startItem.length() + output.length() + endItem.length()
                println('\n' + ('-' * repeatLength) + '\n' + startItem + output + endItem + '\n' + ('-' * repeatLength))
            }
        }
    }
}

Inner text shadow with CSS

More precise explanation of the CSS in kendo451's answer.

There's another way to get a fancy-hacky inner shadow illusion,
which I'll explain in three simple steps. Say we have this HTML:

<h1>Get this</h1>

and this CSS:

h1 {
  color: black;
  background-color: #cc8100;
}

It's a good slogan

Step 1

Let's start by making the text transparent:

h1 {
  color: transparent;
  background-color: #cc8100;
}

It's a box

Step 2

Now, we crop that background to the shape of the text:

h1 {
  color: transparent;
  background-color: #cc8100;
  background-clip: text;
}

The background is the text!

Step 3

Now, the magic: we'll put a blurred text-shadow, which will be in front of the background, thus giving the impression of an inner shadow!

h1 {
  color: transparent;
  background-color: #cc8100;
  background-clip: text;
  text-shadow: 0px 2px 5px #f9c800;
}

We got it! Yay!

See the final result.

Downsides?

  • Only works in Webkit (background-clip can't be text).
  • Multiple shadows? Don't even think.
  • You get an outer glow too.

Oracle get previous day records

Simple solution and understanding

To answer the question:

SELECT field,datetime_field 
FROM database
WHERE TO_CHAR(date_field, 'YYYYMMDD') = TO_CHAR(SYSDATE-1, 'YYYYMMDD');

Some explanation

If you have a field that is not in date format but want to compare using date i.e. field is considered as date but in number format e.g. 20190823 (YYYYMMDD)

SELECT * FROM YOUR_TABLE WHERE ID_DATE = TO_CHAR(SYSDATE-1, 'YYYYMMDD') 

If you have a field that is in date/timestamp format and you need to compare, Just change the format

SELECT TO_CHAR(SYSDATE-1, 'YYYY-MM-DD HH24:MI:SS')  FROM DUAL

IF you want to return it to date format

SELECT TO_DATE(TO_CHAR(SYSDATE-1, 'YYYY-MM-DD HH24:MI:SS'), 'YYYY-MM-DD HH24:MI:SS') AS NEW_DATE  FROM DUAL

Conclusion.

With this knowledge you can convert the filed you want to compare to a YYYYMMDD or YYYY-MM-DD or any year-month-date format then compare with the same sysdate format.

C#: what is the easiest way to subtract time?

Hi if you are going to subtract only Integer value from DateTime then you have to write code like this

DateTime.Now.AddHours(-2)

Here I am subtracting 2 hours from the current date and time

How to unbind a listener that is calling event.preventDefault() (using jQuery)?

The Event interface's preventDefault() method tells the user agent that if the event does not get explicitly handled, its default action should not be taken as it normally would be. The event continues to propagate as usual, unless one of its event listeners calls stopPropagation() or stopImmediatePropagation(), either of which terminates propagation at once.

Calling preventDefault() during any stage of event flow cancels the event, meaning that any default action normally taken by the implementation as a result of the event will not occur.

You can use Event.cancelable to check if the event is cancelable. Calling preventDefault() for a non-cancelable event has no effect.

window.onKeydown = event => {
    /*
        if the control button is pressed, the event.ctrKey 
        will be the value  [true]
    */

    if (event.ctrKey && event.keyCode == 83) {
        event.preventDefault();
        // you function in here.
    }
}

How to get user agent in PHP

Use the native PHP $_SERVER['HTTP_USER_AGENT'] variable instead.

The SELECT permission was denied on the object 'sysobjects', database 'mssqlsystemresource', schema 'sys'

In my case, simply giving the user permissions on the database fixed it.

So Right click on the database -> Click Properties -> [left hand menu] Click Permissions -> and scroll down to Backup database -> Tick "Grant"

Disable a textbox using CSS

CSS cannot disable the textbox, you can however turn off display or visibility.

display: none;
visibility: hidden;

Or you can also set the HTMLattribute:

disabled="disabled"

sql query to get earliest date

SELECT TOP 1 ID, Name, Score, [Date]
FROM myTable
WHERE ID = 2
Order BY [Date]

Draw text in OpenGL ES

In the OpenGL ES 2.0/3.0 you can also combining OGL View and Android's UI-elements:

public class GameActivity extends AppCompatActivity {
    private SurfaceView surfaceView;
    @Override
    protected void onCreate(Bundle state) { 
        setContentView(R.layout.activity_gl);
        surfaceView = findViewById(R.id.oglView);
        surfaceView.init(this.getApplicationContext());
        ...
    } 
}

public class SurfaceView extends GLSurfaceView {
    private SceneRenderer renderer;
    public SurfaceView(Context context) {
        super(context);
    }

    public SurfaceView(Context context, AttributeSet attributes) {
        super(context, attributes);
    }

    public void init(Context context) {
        renderer = new SceneRenderer(context);
        setRenderer(renderer);
        ...
    }
}

Create layout activity_gl.xml:

<?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout
        tools:context=".activities.GameActivity">
    <com.app.SurfaceView
        android:id="@+id/oglView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
    <TextView ... />
    <TextView ... />
    <TextView ... />
</androidx.constraintlayout.widget.ConstraintLayout>

To update elements from the render thread, can use Handler/Looper.

How to get the CPU Usage in C#?

You can use WMI to get CPU percentage information. You can even log into a remote computer if you have the correct permissions. Look at http://www.csharphelp.com/archives2/archive334.html to get an idea of what you can accomplish.

Also helpful might be the MSDN reference for the Win32_Process namespace.

See also a CodeProject example How To: (Almost) Everything In WMI via C#.

Pandas split column of lists into multiple columns

You can use DataFrame constructor with lists created by to_list:

import pandas as pd

d1 = {'teams': [['SF', 'NYG'],['SF', 'NYG'],['SF', 'NYG'],
                ['SF', 'NYG'],['SF', 'NYG'],['SF', 'NYG'],['SF', 'NYG']]}
df2 = pd.DataFrame(d1)
print (df2)
       teams
0  [SF, NYG]
1  [SF, NYG]
2  [SF, NYG]
3  [SF, NYG]
4  [SF, NYG]
5  [SF, NYG]
6  [SF, NYG]

df2[['team1','team2']] = pd.DataFrame(df2.teams.tolist(), index= df2.index)
print (df2)
       teams team1 team2
0  [SF, NYG]    SF   NYG
1  [SF, NYG]    SF   NYG
2  [SF, NYG]    SF   NYG
3  [SF, NYG]    SF   NYG
4  [SF, NYG]    SF   NYG
5  [SF, NYG]    SF   NYG
6  [SF, NYG]    SF   NYG

And for new DataFrame:

df3 = pd.DataFrame(df2['teams'].to_list(), columns=['team1','team2'])
print (df3)
  team1 team2
0    SF   NYG
1    SF   NYG
2    SF   NYG
3    SF   NYG
4    SF   NYG
5    SF   NYG
6    SF   NYG

Solution with apply(pd.Series) is very slow:

#7k rows
df2 = pd.concat([df2]*1000).reset_index(drop=True)

In [121]: %timeit df2['teams'].apply(pd.Series)
1.79 s ± 52.5 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

In [122]: %timeit pd.DataFrame(df2['teams'].to_list(), columns=['team1','team2'])
1.63 ms ± 54.3 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

How can I calculate the difference between two dates?

Checkout this out. It takes care of daylight saving , leap year as it used iOS calendar to calculate.You can change the string and conditions to includes minutes with hours and days.

+(NSString*)remaningTime:(NSDate*)startDate endDate:(NSDate*)endDate
{
    NSDateComponents *components;
    NSInteger days;
    NSInteger hour;
    NSInteger minutes;
    NSString *durationString;

    components = [[NSCalendar currentCalendar] components: NSCalendarUnitDay|NSCalendarUnitHour|NSCalendarUnitMinute fromDate: startDate toDate: endDate options: 0];

    days = [components day];
    hour = [components hour];
    minutes = [components minute];

    if(days>0)
    {
        if(days>1)
            durationString=[NSString stringWithFormat:@"%d days",days];
        else
            durationString=[NSString stringWithFormat:@"%d day",days];
        return durationString;
    }
    if(hour>0)
    {        
        if(hour>1)
            durationString=[NSString stringWithFormat:@"%d hours",hour];
        else
            durationString=[NSString stringWithFormat:@"%d hour",hour];
        return durationString;
    }
    if(minutes>0)
    {
        if(minutes>1)
            durationString = [NSString stringWithFormat:@"%d minutes",minutes];
        else
            durationString = [NSString stringWithFormat:@"%d minute",minutes];

        return durationString;
    }
    return @""; 
}

How do I resolve a path relative to an ASP.NET MVC 4 application root?

I find this code useful when I need a path outside of a controller, such as when I'm initializing components in Global.asax.cs:

HostingEnvironment.MapPath("~/Data/data.html")

public static const in TypeScript

You can use a getter, so that your property is going to be reading only. Example:

export class MyClass {
    private _LEVELS = {
        level1: "level1",
        level2: "level2",
        level2: "level2"
    };

    public get STATUSES() {
        return this._LEVELS;
    }
}

Used in another class:

import { MyClass } from "myclasspath";
class AnotherClass {
    private myClass = new MyClass();

    tryLevel() {
       console.log(this.myClass.STATUSES.level1);
    }
}

Text that shows an underline on hover

<span class="txt">Some Text</span>

.txt:hover {
    text-decoration: underline;
}

Why does modulus division (%) only work with integers?

Because the normal mathematical notion of "remainder" is only applicable to integer division. i.e. division that is required to generate integer quotient.

In order to extend the concept of "remainder" to real numbers you have to introduce a new kind of "hybrid" operation that would generate integer quotient for real operands. Core C language does not support such operation, but it is provided as a standard library fmod function, as well as remainder function in C99. (Note that these functions are not the same and have some peculiarities. In particular, they do not follow the rounding rules of integer division.)

Looping through JSON with node.js

Take a look at Traverse. It will recursively walk an object tree for you and at every node you have a number of different objects you can access - key of current node, value of current node, parent of current node, full key path of current node, etc. https://github.com/substack/js-traverse. I've used it to good effect on objects that I wanted to scrub circular references to and when I need to do a deep clone while transforming various data bits. Here's some code pulled form their samples to give you a flavor of what it can do.

var id = 54;
var callbacks = {};
var obj = { moo : function () {}, foo : [2,3,4, function () {}] };

var scrubbed = traverse(obj).map(function (x) {
    if (typeof x === 'function') {
        callbacks[id] = { id : id, f : x, path : this.path };
        this.update('[Function]');
        id++;
    }
});

console.dir(scrubbed);
console.dir(callbacks);

Pygame Drawing a Rectangle

With the module pygame.draw shapes like rectangles, circles, polygons, liens, ellipses or arcs can be drawn. Some examples:

pygame.draw.rect draws filled rectangular shapes or outlines. The arguments are the target Surface (i.s. the display), the color, the rectangle and the optional outline width. The rectangle argument is a tuple with the 4 components (x, y, width, height), where (x, y) is the upper left point of the rectangle. Alternatively, the argument can be a pygame.Rect object:

pygame.draw.rect(window, color, (x, y, width, height))
rectangle = pygame.Rect(x, y, width, height)
pygame.draw.rect(window, color, rectangle)

pygame.draw.circle draws filled circles or outlines. The arguments are the target Surface (i.s. the display), the color, the center, the radius and the optional outline width. The center argument is a tuple with the 2 components (x, y):

pygame.draw.circle(window, color, (x, y), radius)

pygame.draw.polygon draws filled polygons or contours. The arguments are the target Surface (i.s. the display), the color, a list of points and the optional contour width. Each point is a tuple with the 2 components (x, y):

pygame.draw.polygon(window, color, [(x1, y1), (x2, y2), (x3, y3)])

Minimal example:

import pygame

pygame.init()

window = pygame.display.set_mode((200, 200))
clock = pygame.time.Clock()

run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    window.fill((255, 255, 255))

    pygame.draw.rect(window, (0, 0, 255), (20, 20, 160, 160))
    pygame.draw.circle(window, (255, 0, 0), (100, 100), 80)
    pygame.draw.polygon(window, (255, 255, 0), 
        [(100, 20), (100 + 0.8660 * 80, 140), (100 - 0.8660 * 80, 140)])

    pygame.display.flip()

pygame.quit()
exit()

Cannot connect to the Docker daemon on macOS

I have Mac OS and I open Launchpad and select docker application. from reset tab click on restart.

Android dependency has different version for the compile and runtime

This worked for me:

Add the follow line in app/build.gradle in dependencies section:

implementation "com.android.support:appcompat-v7:27.1.0"

or :27.1.1 in my case

Select rows having 2 columns equal value

For question 1:

SELECT DISTINCT a.*
  FROM [Table] a
  INNER JOIN
  [Table] b
  ON
  a.C1 <> b.C1 AND a.C2 = b.C2 AND a.C3 = b.C3 AND a.C4 = b.C4

Using an inner join is much more efficient than a subquery because it requires fewer operations, and maintains the use of indexes when comparing the values, allowing the SQL server to better optimize the query before its run. Using appropriate indexes with this query can bring your query down to only n * log(n) rows to compare.

Using a subquery with your where clause or only doing a standard join where C1 does not equal C2 results in a table that has roughly 2 to the power of n rows to compare, where n is the number of rows in the table.

So by using proper indexing with an Inner Join, which only returns records which met the join criteria, we're able to drastically improve the performance. Also note that we return DISTINCT a.*, because this will only return the columns for table a where the join criteria was met. Returning * would return the columns for both a and b where the criteria was met, and not including DISTINCT would result in a duplicate of each row for each time that row row matched another row more than once.

A similar approach could also be performed using CROSS APPLY, which still uses a subquery, but makes use of indexes more efficiently.

An implementation with the keyword USING instead of ON could also work, but the syntax is more complicated to make work because your want to match on rows where C1 does not match, so you would need an additional where clause to filter out matching each row with itself. Also, USING is not compatible/allowed in conjunction with table values in all implementations of SQL, so it's best to stick with ON.

Similarly, for question 2:

SELECT DISTINCT a.*
  FROM [Table] a
  INNER JOIN
  [Table] b
  ON
  a.C1 <> b.C1 AND a.C4 = b.C4

This is essentially the same query as for 1, but because it only wants to know which rows match for C4, we only compare on the rows for C4.

Streaming a video file to an html5 video player with Node.js so that the video controls continue to work?

The Accept Ranges header (the bit in writeHead()) is required for the HTML5 video controls to work.

I think instead of just blindly send the full file, you should first check the Accept Ranges header in the REQUEST, then read in and send just that bit. fs.createReadStream support start, and end option for that.

So I tried an example and it works. The code is not pretty but it is easy to understand. First we process the range header to get the start/end position. Then we use fs.stat to get the size of the file without reading the whole file into memory. Finally, use fs.createReadStream to send the requested part to the client.

var fs = require("fs"),
    http = require("http"),
    url = require("url"),
    path = require("path");

http.createServer(function (req, res) {
  if (req.url != "/movie.mp4") {
    res.writeHead(200, { "Content-Type": "text/html" });
    res.end('<video src="http://localhost:8888/movie.mp4" controls></video>');
  } else {
    var file = path.resolve(__dirname,"movie.mp4");
    fs.stat(file, function(err, stats) {
      if (err) {
        if (err.code === 'ENOENT') {
          // 404 Error if file not found
          return res.sendStatus(404);
        }
      res.end(err);
      }
      var range = req.headers.range;
      if (!range) {
       // 416 Wrong range
       return res.sendStatus(416);
      }
      var positions = range.replace(/bytes=/, "").split("-");
      var start = parseInt(positions[0], 10);
      var total = stats.size;
      var end = positions[1] ? parseInt(positions[1], 10) : total - 1;
      var chunksize = (end - start) + 1;

      res.writeHead(206, {
        "Content-Range": "bytes " + start + "-" + end + "/" + total,
        "Accept-Ranges": "bytes",
        "Content-Length": chunksize,
        "Content-Type": "video/mp4"
      });

      var stream = fs.createReadStream(file, { start: start, end: end })
        .on("open", function() {
          stream.pipe(res);
        }).on("error", function(err) {
          res.end(err);
        });
    });
  }
}).listen(8888);

How to remove array element in mongodb?

This below code will remove the complete object element from the array, where the phone number is '+1786543589455'

db.collection.update(
  { _id: id },
  { $pull: { 'contact': { number: '+1786543589455' } } }
);

Definition of a Balanced Tree

  1. The height of a node in a tree is the length of the longest path from that node downward to a leaf, counting both the start and end vertices of the path.
  2. A node in a tree is height-balanced if the heights of its subtrees differ by no more than 1.
  3. A tree is height-balanced if all of its nodes are height-balanced.

Is it possible to pass parameters programmatically in a Microsoft Access update query?

I just tested this and it works in Access 2010.

Say you have a SELECT query with parameters:

PARAMETERS startID Long, endID Long;
SELECT Members.*
FROM Members
WHERE (((Members.memberID) Between [startID] And [endID]));

You run that query interactively and it prompts you for [startID] and [endID]. That works, so you save that query as [MemberSubset].

Now you create an UPDATE query based on that query:

UPDATE Members SET Members.age = [age]+1
WHERE (((Members.memberID) In (SELECT memberID FROM [MemberSubset])));

You run that query interactively and again you are prompted for [startID] and [endID] and it works well, so you save it as [MemberSubsetUpdate].

You can run [MemberSubsetUpdate] from VBA code by specifying [startID] and [endID] values as parameters to [MemberSubsetUpdate], even though they are actually parameters of [MemberSubset]. Those parameter values "trickle down" to where they are needed, and the query does work without human intervention:

Sub paramTest()
    Dim qdf As DAO.QueryDef
    Set qdf = CurrentDb.QueryDefs("MemberSubsetUpdate")
    qdf!startID = 1  ' specify
    qdf!endID = 2    '     parameters
    qdf.Execute
    Set qdf = Nothing
End Sub

Django: Display Choice Value

Others have pointed out that a get_FOO_display method is what you need. I'm using this:

def get_type(self):
    return [i[1] for i in Item._meta.get_field('type').choices if i[0] == self.type][0]

which iterates over all of the choices that a particular item has until it finds the one that matches the items type

Java - creating a new thread

There are several ways to create a thread

  1. by extending Thread class >5
  2. by implementing Runnable interface - > 5
  3. by using ExecutorService inteface - >=8

Is it possible to simulate key press events programmatically?

This is what I managed to find:

_x000D_
_x000D_
function createKeyboardEvent(name, key, altKey, ctrlKey, shiftKey, metaKey, bubbles) {
  var e = new Event(name)
  e.key = key
  e.keyCode = e.key.charCodeAt(0)
  e.which = e.keyCode
  e.altKey = altKey
  e.ctrlKey = ctrlKey
  e.shiftKey = shiftKey
  e.metaKey =  metaKey
  e.bubbles = bubbles
  return e
}

var name = 'keydown'
var key = 'a'

var event = createKeyboardEvent(name, key, false, false, false, false, true)

document.addEventListener(name, () => {})
document.dispatchEvent(event)
_x000D_
_x000D_
_x000D_

Excel VBA Open a Folder

If you want to open a windows file explorer, you should call explorer.exe

Call Shell("explorer.exe" & " " & "P:\Engineering", vbNormalFocus)

Equivalent syxntax

Shell "explorer.exe" & " " & "P:\Engineering", vbNormalFocus

C program to check little vs. big endian

In short, yes.

Suppose we are on a 32-bit machine.

If it is little endian, the x in the memory will be something like:

       higher memory
          ----->
    +----+----+----+----+
    |0x01|0x00|0x00|0x00|
    +----+----+----+----+
    A
    |
   &x

so (char*)(&x) == 1, and *y+48 == '1'.

If it is big endian, it will be:

    +----+----+----+----+
    |0x00|0x00|0x00|0x01|
    +----+----+----+----+
    A
    |
   &x

so this one will be '0'.

Read file content from S3 bucket with boto3

You might also consider the smart_open module, which supports iterators:

from smart_open import smart_open

# stream lines from an S3 object
for line in smart_open('s3://mybucket/mykey.txt', 'rb'):
    print(line.decode('utf8'))

and context managers:

with smart_open('s3://mybucket/mykey.txt', 'rb') as s3_source:
    for line in s3_source:
         print(line.decode('utf8'))

    s3_source.seek(0)  # seek to the beginning
    b1000 = s3_source.read(1000)  # read 1000 bytes

Find smart_open at https://pypi.org/project/smart_open/

How to check if ZooKeeper is running or up from command prompt?

I use:

  jps

Depending on your installation a running Zookeeper would look like

  HQuorumPeer

or sth. with zookeeper in it's name.

How to make a Bootstrap accordion collapse when clicking the header div?

All you need to do is to to use...

  • data-toggle="collapse"
  • data-target="#ElementToExpandOnClick"

...on the element you want to click to trigger the collapse/expand effect.

The element with data-toggle="collapse" will be the element to trigger the effect. The data-target attribute indicates the element that will expand when the effect is triggered.

Optionally you can set the data-parent if you want to create an accordion effect instead of independent collapsible, e.g.:

  • data-parent="#accordion"

I would also add the following CSS to the elements with data-toggle="collapse" if they aren't <a> tags, e.g.:

.panel-heading {
    cursor: pointer;
}

Here's a jsfiddle with the modified html from the Bootstrap 3 documentation.

Loop through a date range with JavaScript

Let us assume you got the start date and end date from the UI and stored it in the scope variable in the controller.

Then declare an array which will get reset on every function call so that on the next call for the function the new data can be stored.

var dayLabel = [];

Remember to use new Date(your starting variable) because if you dont use the new date and directly assign it to variable the setDate function will change the origional variable value in each iteration`

for (var d = new Date($scope.startDate); d <= $scope.endDate; d.setDate(d.getDate() + 1)) {
                dayLabel.push(new Date(d));
            }

How to move git repository with all branches from bitbucket to github?

There is the Importing a repository with GitHub Importer

If you have a project hosted on another version control system as Mercurial, you can automatically import it to GitHub using the GitHub Importer tool.

  1. In the upper-right corner of any page, click , and then click Import repository.
  2. Under "Your old repository's clone URL", type the URL of the project you want to import.
  3. Choose your user account or an organization to own the repository, then type a name for the repository on GitHub.
  4. Specify whether the new repository should be public or private.
    • Public repositories are visible to any user on GitHub, so you can benefit from GitHub's collaborative community.
    • Public or private repository radio buttonsPrivate repositories are only available to the repository owner, as well as any collaborators you choose to share with.
  5. Review the information you entered, then click Begin import.

You'll receive an email when the repository has been completely imported.

  1. https://help.github.com/categories/importing-your-projects-to-github
  2. https://help.github.com/articles/importing-a-repository-with-github-importer/

How to import JSON File into a TypeScript file?

In angular7, I simply used

let routesObject = require('./routes.json');

My routes.json file looks like this

{

    "routeEmployeeList":    "employee-list",
    "routeEmployeeDetail":      "employee/:id"
}

You access json items using

routesObject.routeEmployeeList

How to count number of records per day?

You could also try this:

SELECT DISTINCT (DATE(dateadded)) AS unique_date, COUNT(*) AS amount
FROM table
GROUP BY unique_date
ORDER BY unique_date ASC

Cloning a private Github repo

This worked for me on mac git clone https://[email protected]:username/repo_name

PHP foreach change original array values

Use &:

foreach($arr as &$value) {
    $value = $newVal;
}

& passes a value of the array as a reference and does not create a new instance of the variable. Thus if you change the reference the original value will change.

PHP documentation for Passing by Reference

Edit 2018

This answer seems to be favored by a lot of people on the internet, which is why I decided to add more information and words of caution.
While pass by reference in foreach (or functions) is a clean and short solution, for many beginners this might be a dangerous pitfall.

  1. Loops in PHP don't have their own scope. - @Mark Amery

    This could be a serious problem when the variables are being reused in the same scope. Another SO question nicely illustrates why that might be a problem.

  2. As foreach relies on the internal array pointer in PHP 5, changing it within the loop may lead to unexpected behavior. - PHP docs for foreach.

    Unsetting a record or changing the hash value (the key) during the iteration on the same loop could lead to potentially unexpected behaviors in PHP < 7. The issue gets even more complicated when the array itself is a reference.

  3. Foreach performance.
    In general, PHP prefers pass by value due to the copy-on-write feature. It means that internally PHP will not create duplicate data unless the copy of it needs to be changed. It is debatable whether pass by reference in foreach would offer a performance improvement. As it is always the case, you need to test your specific scenario and determine which option uses less memory and CPU time. For more information see the SO post linked below by NikiC.

  4. Code readability.
    Creating references in PHP is something that quickly gets out of hand. If you are a novice and don't have full control of what you are doing, it is best to stay away from references. For more information about & operator take a look at this guide: Reference — What does this symbol mean in PHP?
    For those who want to learn more about this part of PHP language: PHP References Explained

A very nice technical explanation by @NikiC of the internal logic of PHP foreach loops:
How does PHP 'foreach' actually work?

How can I delete using INNER JOIN with SQL Server?

 DELETE a FROM WorkRecord2 a 
       INNER JOIN Employee b 
       ON a.EmployeeRun = b.EmployeeNo 
       Where a.Company = '1' 
       AND a.Date = '2013-05-06'

HTTP POST with URL query parameters -- good idea or not?

I agree - it's probably safer to use a GET request if you're just passing data in the URL and not in the body. See this similar question for some additional views on the whole POST+GET concept.

Session variables not working php

Maybe if your session path is not working properly you can try session.save_path(path/to/any folder); function as alternative path. If it works you can ask your hosting provider about default path issue.

Installing Android Studio, does not point to a valid JVM installation error

Recently I am working with the 1.8.0_25 JDK version on Windows 8.1 and I had the same problem with this. But as PankaJ Jakhar said

The real solution for me was pretty simple:

  1. Add the JAVA_HOME variable to the system ones, not on the user ones.
  2. The path I introduced for this variable was:

    C:\Program Files\Java\jdk1.8.0_25\
    

And it works for me!

Angular 5 Scroll to top on every Route click

In my case I just added

window.scroll(0,0);

in ngOnInit() and its working fine.

C# IPAddress from string

You've probably miss-typed something above that bit of code or created your own class called IPAddress. If you're using the .net one, that function should be available.

Have you tried using System.Net.IPAddress just in case?

System.Net.IPAddress ipaddress = System.Net.IPAddress.Parse("127.0.0.1");  //127.0.0.1 as an example

The docs on Microsoft's site have a complete example which works fine on my machine.

Python re.sub(): how to substitute all 'u' or 'U's with 'you'

Use a special character \b, which matches empty string at the beginning or at the end of a word:

print re.sub(r'\b[uU]\b', 'you', text)

spaces are not a reliable solution because there are also plenty of other punctuation marks, so an abstract character \b was invented to indicate a word's beginning or end.

Anonymous method in Invoke call

You need to create a delegate type. The keyword 'delegate' in the anonymous method creation is a bit misleading. You are not creating an anonymous delegate but an anonymous method. The method you created can be used in a delegate. Like this:

myControl.Invoke(new MethodInvoker(delegate() { (MyMethod(this, new MyEventArgs(someParameter)); }));

How do you clear a slice in Go?

Setting the slice to nil is the best way to clear a slice. nil slices in go are perfectly well behaved and setting the slice to nil will release the underlying memory to the garbage collector.

See playground

package main

import (
    "fmt"
)

func dump(letters []string) {
    fmt.Println("letters = ", letters)
    fmt.Println(cap(letters))
    fmt.Println(len(letters))
    for i := range letters {
        fmt.Println(i, letters[i])
    }
}

func main() {
    letters := []string{"a", "b", "c", "d"}
    dump(letters)
    // clear the slice
    letters = nil
    dump(letters)
    // add stuff back to it
    letters = append(letters, "e")
    dump(letters)
}

Prints

letters =  [a b c d]
4
4
0 a
1 b
2 c
3 d
letters =  []
0
0
letters =  [e]
1
1
0 e

Note that slices can easily be aliased so that two slices point to the same underlying memory. The setting to nil will remove that aliasing.

This method changes the capacity to zero though.

get current date and time in groovy?

Date has the time part, so we only need to extract it from Date

I personally prefer the default format parameter of the Date when date and time needs to be separated instead of using the extra SimpleDateFormat

Date date = new Date()
String datePart = date.format("dd/MM/yyyy")
String timePart = date.format("HH:mm:ss")

println "datePart : " + datePart + "\ttimePart : " + timePart

How to git reset --hard a subdirectory?

What about

subdir=thesubdir
for fn in $(find $subdir); do
  git ls-files --error-unmatch $fn 2>/dev/null >/dev/null;
  if [ "$?" = "1" ]; then
    continue;
  fi
  echo "Restoring $fn";
  git show HEAD:$fn > $fn;
done 

How can I set size of a button?

This is how I did it.

            JFrame.setDefaultLookAndFeelDecorated(true);
            JDialog.setDefaultLookAndFeelDecorated(true);
            JFrame frame = new JFrame("SAP Multiple Entries");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            JPanel panel = new JPanel(new GridLayout(10,10,10,10));
            frame.setLayout(new FlowLayout());
            frame.setSize(512, 512);
            JButton button = new JButton("Select File");
            button.setPreferredSize(new Dimension(256, 256));
            panel.add(button);

            button.addActionListener(new ActionListener() {

                public void actionPerformed(ActionEvent ae) {
                    JFileChooser fileChooser = new JFileChooser();
                    int returnValue = fileChooser.showOpenDialog(null);
                    if (returnValue == JFileChooser.APPROVE_OPTION) {
                        File selectedFile = fileChooser.getSelectedFile();

                        keep = selectedFile.getAbsolutePath();


                       // System.out.println(keep);
                        //out.println(file.flag); 
                       if(file.flag==true) {
                           JOptionPane.showMessageDialog(null, "It is done! \nLocation: " + file.path , "Success Message", JOptionPane.INFORMATION_MESSAGE);
                       }
                       else{
                           JOptionPane.showMessageDialog(null, "failure", "not okay", JOptionPane.INFORMATION_MESSAGE);
                       }
                    }
                }
            });
            frame.add(button);
            frame.pack();
            frame.setVisible(true);

What's the difference between Docker Compose vs. Dockerfile

In my workflow, I add a Dockerfile for each part of my system and configure it that each part could run individually. Then I add a docker-compose.yml to bring them together and link them.

Biggest advantage (in my opinion): when linking the containers, you can define a name and ping your containers with this name. Therefore your database might be accessible with the name db and no longer by its IP.

How can I declare optional function parameters in JavaScript?

With ES6: This is now part of the language:

function myFunc(a, b = 0) {
   // function body
}

Please keep in mind that ES6 checks the values against undefined and not against truthy-ness (so only real undefined values get the default value - falsy values like null will not default).


With ES5:

function myFunc(a,b) {
  b = b || 0;

  // b will be set either to b or to 0.
}

This works as long as all values you explicitly pass in are truthy. Values that are not truthy as per MiniGod's comment: null, undefined, 0, false, ''

It's pretty common to see JavaScript libraries to do a bunch of checks on optional inputs before the function actually starts.

how to release localhost from Error: listen EADDRINUSE

I have solved this issue by adding below in my package.json for killing active PORT - 4000 (in my case) Running on WSL2/Linux/Mac

"scripts": {
    "dev": "nodemon app.js",
    "predev":"fuser -k 4000/tcp && echo 'Terminated' || echo 'Nothing was running on the PORT'",
  }

Source

Iterating through a JSON object

Your loading of the JSON data is a little fragile. Instead of:

json_raw= raw.readlines()
json_object = json.loads(json_raw[0])

you should really just do:

json_object = json.load(raw)

You shouldn't think of what you get as a "JSON object". What you have is a list. The list contains two dicts. The dicts contain various key/value pairs, all strings. When you do json_object[0], you're asking for the first dict in the list. When you iterate over that, with for song in json_object[0]:, you iterate over the keys of the dict. Because that's what you get when you iterate over the dict. If you want to access the value associated with the key in that dict, you would use, for example, json_object[0][song].

None of this is specific to JSON. It's just basic Python types, with their basic operations as covered in any tutorial.

Assign width to half available screen width declaratively

give width as 0dp to make sure its size is exactly as per its weight this will make sure that even if content of child views get bigger, they'll still be limited to exactly half(according to is weight)

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:weightSum="1"
     >

    <Button
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:text="click me"
    android:layout_weight="0.5"/>


    <TextView
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:text="Hello World"
    android:layout_weight="0.5"/>
  </LinearLayout>

org.json.simple.JSONArray cannot be cast to org.json.simple.JSONObject

use your jsonsimpleobject direclty like below

JSONObject unitsObj = parser.parse(new FileReader("file.json");

What is Express.js?

1) What is Express.js?

Express.js is a Node.js framework. It's the most popular framework as of now (the most starred on NPM).

Enter image description here.

It's built around configuration and granular simplicity of Connect middleware. Some people compare Express.js to Ruby Sinatra vs. the bulky and opinionated Ruby on Rails.

2) What is the purpose of it with Node.js?

That you don't have to repeat same code over and over again. Node.js is a low-level I/O mechanism which has an HTTP module. If you just use an HTTP module, a lot of work like parsing the payload, cookies, storing sessions (in memory or in Redis), selecting the right route pattern based on regular expressions will have to be re-implemented. With Express.js, it is just there for you to use.

3) Why do we actually need Express.js? How it is useful for us to use with Node.js?

The first answer should answer your question. If no, then try to write a small REST API server in plain Node.js (that is, using only core modules) and then in Express.js. The latter will take you 5-10x less time and lines of code.

What is Redis? Does it come with Express.js?

Redis is a fast persistent key-value storage. You can optionally use it for storing sessions with Express.js, but you don't need to. By default, Express.js has memory storage for sessions. Redis also can be use for queueing jobs, for example, email jobs.

Check out my tutorial on REST API server with Express.js.

MVC but not by itself

Express.js is not an model-view-controller framework by itself. You need to bring your own object-relational mapping libraries such as Mongoose for MongoDB, Sequelize (http://sequelizejs.com) for SQL databases, Waterline (https://github.com/balderdashy/waterline) for many databases into the stack.

Alternatives

Other Node.js frameworks to consider (https://www.quora.com/Node-js/Which-Node-js-framework-is-best-for-building-a-RESTful-API):

UPDATE: I put together this resource that aid people in choosing Node.js frameworks: http://nodeframework.com

UPDATE2: We added some GitHub stats to nodeframework.com so now you can compare the level of social proof (GitHub stars) for 30+ frameworks on one page.

enter image description here

Full-stack:

Just REST API:

Ruby on Rails like:

Sinatra like:

Other:

Middleware:

Static site generators:

what's the easiest way to put space between 2 side-by-side buttons in asp.net

I used &nbsp; and it is working fine. You could try it. You do not need to use the quotation marks

Docker-Compose can't connect to Docker Daemon

I had the same issue. After taking notes and analyzing some debugging results, finally, I solved what can be the same error. Start the service first,

service docker start

Don't forget to include your user to the docker group.

ASP.NET MVC 3 Razor - Adding class to EditorFor

There isn't any EditorFor override that lets you pass in an anonymous object whose properties would somehow get added as attributes on some tag, especially for the built-in editor templates. You would need to write your own custom editor template and pass the value you want as additional viewdata.

How to get a Fragment to remove itself, i.e. its equivalent of finish()?

You can use the approach below, it works fine:

getActivity().getSupportFragmentManager().popBackStack();

Android and setting width and height programmatically in dp units

I know this is an old question however I've found a much neater way of doing this conversion.

Java

TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 65, getResources().getDisplayMetrics());

Kotlin

TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 65f, resources.displayMetrics)

How to convert string to double with proper cultureinfo

I took some help from MSDN, but this is my answer:

double number;
string localStringNumber;
string doubleNumericValueasString = "65.89875";
System.Globalization.NumberStyles style = System.Globalization.NumberStyles.AllowDecimalPoint;

if (double.TryParse(doubleNumericValueasString, style, System.Globalization.CultureInfo.InvariantCulture, out number))
    Console.WriteLine("Converted '{0}' to {1}.", doubleNumericValueasString, number);
else
    Console.WriteLine("Unable to convert '{0}'.", doubleNumericValueasString);
localStringNumber =number.ToString(System.Globalization.CultureInfo.CreateSpecificCulture("de-DE"));

Remove ALL white spaces from text

Using String.prototype.replace with regex, as mentioned in the other answers, is certainly the best solution.

But, just for fun, you can also remove all whitespaces from a text by using String.prototype.split and String.prototype.join:

_x000D_
_x000D_
const text = ' a b    c d e   f g   ';_x000D_
const newText = text.split(/\s/).join('');_x000D_
_x000D_
console.log(newText); // prints abcdefg
_x000D_
_x000D_
_x000D_

How to remove whitespace from a string in typescript?

Problem

The trim() method removes whitespace from both sides of a string.

Source

Solution

You can use a Javascript replace method to remove white space like

"hello world".replace(/\s/g, "");

Example

_x000D_
_x000D_
var out = "hello world".replace(/\s/g, "");_x000D_
console.log(out);
_x000D_
_x000D_
_x000D_

Calling a JavaScript function named in a variable

Definitely avoid using eval to do something like this, or you will open yourself to XSS (Cross-Site Scripting) vulnerabilities.

For example, if you were to use the eval solutions proposed here, a nefarious user could send a link to their victim that looked like this:

http://yoursite.com/foo.html?func=function(){alert('Im%20In%20Teh%20Codez');}

And their javascript, not yours, would get executed. This code could do something far worse than just pop up an alert of course; it could steal cookies, send requests to your application, etc.

So, make sure you never eval untrusted code that comes in from user input (and anything on the query string id considered user input). You could take user input as a key that will point to your function, but make sure that you don't execute anything if the string given doesn't match a key in your object. For example:

// set up the possible functions:
var myFuncs = {
  func1: function () { alert('Function 1'); },
  func2: function () { alert('Function 2'); },
  func3: function () { alert('Function 3'); },
  func4: function () { alert('Function 4'); },
  func5: function () { alert('Function 5'); }
};
// execute the one specified in the 'funcToRun' variable:
myFuncs[funcToRun]();

This will fail if the funcToRun variable doesn't point to anything in the myFuncs object, but it won't execute any code.

Angular 2 change event - model changes

If this helps you,

<input type="checkbox"  (ngModelChange)="mychange($event)" [ngModel]="mymodel">

mychange(val)
{
   console.log(val); // updated value
}

Android getActivity() is undefined

You want getActivity() inside your class. It's better to use

yourclassname.this.getActivity()

Try this. It's helpful for you.

Export to csv/excel from kibana

To export data to csv/excel from Kibana follow the following steps:-

  1. Click on Visualize Tab & select a visualization (if created). If not created create a visualziation.

  2. Click on caret symbol (^) which is present at the bottom of the visualization.

  3. Then you will get an option of Export:Raw Formatted as the bottom of the page.

Please find below attached image showing Export option after clicking on caret symbol.

Please find below attached image showing Export option after clicking on caret symbol.

How to define multiple CSS attributes in jQuery?

Pass it as an Object:

$(....).css({
    'property': 'value', 
    'property': 'value'
});

http://docs.jquery.com/CSS/css#properties

Python get current time in right timezone

To get the current time in the local timezone as a naive datetime object:

from datetime import datetime
naive_dt = datetime.now()

If it doesn't return the expected time then it means that your computer is misconfigured. You should fix it first (it is unrelated to Python).

To get the current time in UTC as a naive datetime object:

naive_utc_dt = datetime.utcnow()

To get the current time as an aware datetime object in Python 3.3+:

from datetime import datetime, timezone

utc_dt = datetime.now(timezone.utc) # UTC time
dt = utc_dt.astimezone() # local time

To get the current time in the given time zone from the tz database:

import pytz

tz = pytz.timezone('Europe/Berlin')
berlin_now = datetime.now(tz)

It works during DST transitions. It works if the timezone had different UTC offset in the past i.e., it works even if the timezone corresponds to multiple tzinfo objects at different times.

SQL Server: how to select records with specific date from datetime column

SELECT *
FROM LogRequests
WHERE cast(dateX as date) between '2014-05-09' and '2014-05-10';

This will select all the data between the 2 dates

vertical alignment of text element in SVG

attr("dominant-baseline", "central")

How to change the locale in chrome browser

Open chrome, go to chrome://settings/languages

On the left, you should see a list of languages. Use mouse to drag the language you want to the top, that will change the order for the values in Accept-language of requests.

If you still don't see the language you prefer, it may be cookies. Go to cookies and clean it up you should be good.

How to convert a file into a dictionary?

def get_pair(line):
    key, sep, value = line.strip().partition(" ")
    return int(key), value

with open("file.txt") as fd:    
    d = dict(get_pair(line) for line in fd)

How to truncate text in Angular2?

If you want to truncate by a number of words and add an ellipsis you can use this function:

truncate(value: string, limit: number = 40, trail: String = '…'): string {
  let result = value || '';

  if (value) {
    const words = value.split(/\s+/);
    if (words.length > Math.abs(limit)) {
      if (limit < 0) {
        limit *= -1;
        result = trail + words.slice(words.length - limit, words.length).join(' ');
      } else {
        result = words.slice(0, limit).join(' ') + trail;
      }
    }
  }

  return result;
}

Example:

truncate('Bacon ipsum dolor amet sirloin tri-tip swine', 5, '…')
> "Bacon ipsum dolor amet sirloin…"

taken from: https://github.com/yellowspot/ng2-truncate/blob/master/src/truncate-words.pipe.ts

If you want to truncate by a number of letters but don't cut words out use this:

truncate(value: string, limit = 25, completeWords = true, ellipsis = '…') {
  let lastindex = limit;
  if (completeWords) {
    lastindex = value.substr(0, limit).lastIndexOf(' ');
  }
  return `${value.substr(0, limit)}${ellipsis}`;
}

Example:

truncate('Bacon ipsum dolor amet sirloin tri-tip swine', 19, true, '…')
> "Bacon ipsum dolor…"

truncate('Bacon ipsum dolor amet sirloin tri-tip swine', 19, false, '…')
> "Bacon ipsum dolor a…"

How do I copy a folder from remote to local using scp?

scp -r [email protected]:/path/to/foo /home/user/Desktop/

By not including the trailing '/' at the end of foo, you will copy the directory itself (including contents), rather than only the contents of the directory.

From man scp (See online manual)

-r Recursively copy entire directories

Java GUI frameworks. What to choose? Swing, SWT, AWT, SwingX, JGoodies, JavaFX, Apache Pivot?

Swing + SwingX + Miglayout is my combination of choice. Miglayout is so much simpler than Swings perceived 200 different layout managers and much more powerful. Also, it provides you with the ability to "debug" your layouts, which is especially handy when creating complex layouts.

Javascript: best Singleton pattern

Why use a constructor and prototyping for a single object?

The above is equivalent to:

var earth= {
    someMethod: function () {
        if (console && console.log)
            console.log('some method');                             
    }
};
privateFunction1();
privateFunction2();

return {
    Person: Constructors.Person,
    PlanetEarth: earth
};

How to paginate with Mongoose in Node.js?

You can chain just like that:

var query = Model.find().sort('mykey', 1).skip(2).limit(5)

Execute the query using exec

query.exec(callback);

How can I "reset" an Arduino board?

I had this issue as well. I tried the above methods and none seemed to work, however something that did work (somehow, not sure if it was just a freak thing or it is actually a way to do it) was:

  1. Unplug USB from the Arduino
  2. Press and hold the reset button
  3. Plug in USB and power up
  4. Continue holding and upload the sketch. Once it's done uploading, release the reset button.

Correct way to create rounded corners in Twitter Bootstrap

Without less, ans simply for a given div :

In a css :

.footer {
background-color: #ab0000;
padding-top: 40px;
padding-bottom: 10px;
border-radius:5px;
}

In html :

 <div class="footer">
        <p>blablabla</p>
      </div>

getting "No column was specified for column 2 of 'd'" in sql server cte?

Quite an intuitive error message - just need to give the columns in d names

Change to either this

d as 
 (
  select                 
     [duration] = month(clothdeliverydate),                 
     [bkdqty] = SUM(CONVERT(INT, deliveredqty))             
  FROM                 
     barcodetable            
  where                 
     month(clothdeliverydate) is not null                
  group by month(clothdeliverydate)           
 ) 

Or you can explicitly declare the fields in the definition of the cte:

d ([duration], [bkdqty]) as 
 (
  select                 
     month(clothdeliverydate),                 
     SUM(CONVERT(INT, deliveredqty))             
  FROM                 
     barcodetable            
  where                 
     month(clothdeliverydate) is not null                
  group by month(clothdeliverydate)           
 ) 

Qt - reading from a text file

You have to replace string line

QString line = in.readLine();

into while:

QFile file("/home/hamad/lesson11.txt");
if(!file.open(QIODevice::ReadOnly)) {
    QMessageBox::information(0, "error", file.errorString());
}

QTextStream in(&file);

while(!in.atEnd()) {
    QString line = in.readLine();    
    QStringList fields = line.split(",");    
    model->appendRow(fields);    
}

file.close();

Loading a properties file from Java package

When loading the Properties from a Class in the package com.al.common.email.templates you can use

Properties prop = new Properties();
InputStream in = getClass().getResourceAsStream("foo.properties");
prop.load(in);
in.close();

(Add all the necessary exception handling).

If your class is not in that package, you need to aquire the InputStream slightly differently:

InputStream in = 
 getClass().getResourceAsStream("/com/al/common/email/templates/foo.properties");

Relative paths (those without a leading '/') in getResource()/getResourceAsStream() mean that the resource will be searched relative to the directory which represents the package the class is in.

Using java.lang.String.class.getResource("foo.txt") would search for the (inexistent) file /java/lang/String/foo.txt on the classpath.

Using an absolute path (one that starts with '/') means that the current package is ignored.

Passing variable from Form to Module in VBA

Don't declare the variable in the userform. Declare it as Public in the module.

Public pass As String

In the Userform

Private Sub CommandButton1_Click()
    pass = UserForm1.TextBox1
    Unload UserForm1
End Sub

In the Module

Public pass As String

Public Sub Login()
    '
    '~~> Rest of the code
    '
    UserForm1.Show
    driver.findElementByName("PASSWORD").SendKeys pass
    '
    '~~> Rest of the code
    '
End Sub

You might want to also add an additional check just before calling the driver.find... line?

If Len(Trim(pass)) <> 0 Then

This will ensure that a blank string is not passed.

What is the runtime performance cost of a Docker container?

Here's some more benchmarks for Docker based memcached server versus host native memcached server using Twemperf benchmark tool https://github.com/twitter/twemperf with 5000 connections and 20k connection rate

Connect time overhead for docker based memcached seems to agree with above whitepaper at roughly twice native speed.

Twemperf Docker Memcached

Connection rate: 9817.9 conn/s
Connection time [ms]: avg 341.1 min 73.7 max 396.2 stddev 52.11
Connect time [ms]: avg 55.0 min 1.1 max 103.1 stddev 28.14
Request rate: 83942.7 req/s (0.0 ms/req)
Request size [B]: avg 129.0 min 129.0 max 129.0 stddev 0.00
Response rate: 83942.7 rsp/s (0.0 ms/rsp)
Response size [B]: avg 8.0 min 8.0 max 8.0 stddev 0.00
Response time [ms]: avg 28.6 min 1.2 max 65.0 stddev 0.01
Response time [ms]: p25 24.0 p50 27.0 p75 29.0
Response time [ms]: p95 58.0 p99 62.0 p999 65.0

Twemperf Centmin Mod Memcached

Connection rate: 11419.3 conn/s
Connection time [ms]: avg 200.5 min 0.6 max 263.2 stddev 73.85
Connect time [ms]: avg 26.2 min 0.0 max 53.5 stddev 14.59
Request rate: 114192.6 req/s (0.0 ms/req)
Request size [B]: avg 129.0 min 129.0 max 129.0 stddev 0.00
Response rate: 114192.6 rsp/s (0.0 ms/rsp)
Response size [B]: avg 8.0 min 8.0 max 8.0 stddev 0.00
Response time [ms]: avg 17.4 min 0.0 max 28.8 stddev 0.01
Response time [ms]: p25 12.0 p50 20.0 p75 23.0
Response time [ms]: p95 28.0 p99 28.0 p999 29.0

Here's bencmarks using memtier benchmark tool

memtier_benchmark docker Memcached

4         Threads
50        Connections per thread
10000     Requests per thread
Type        Ops/sec     Hits/sec   Misses/sec      Latency       KB/sec
------------------------------------------------------------------------
Sets       16821.99          ---          ---      1.12600      2271.79
Gets      168035.07    159636.00      8399.07      1.12000     23884.00
Totals    184857.06    159636.00      8399.07      1.12100     26155.79

memtier_benchmark Centmin Mod Memcached

4         Threads
50        Connections per thread
10000     Requests per thread
Type        Ops/sec     Hits/sec   Misses/sec      Latency       KB/sec
------------------------------------------------------------------------
Sets       28468.13          ---          ---      0.62300      3844.59
Gets      284368.51    266547.14     17821.36      0.62200     39964.31
Totals    312836.64    266547.14     17821.36      0.62200     43808.90

Position Absolute + Scrolling

So gaiour is right, but if you're looking for a full height item that doesn't scroll with the content, but is actually the height of the container, here's the fix. Have a parent with a height that causes overflow, a content container that has a 100% height and overflow: scroll, and a sibling then can be positioned according to the parent size, not the scroll element size. Here is the fiddle: http://jsfiddle.net/M5cTN/196/

and the relevant code:

html:

<div class="container">
  <div class="inner">
    Lorem ipsum ...
  </div>
  <div class="full-height"></div>
</div>

css:

.container{
  height: 256px;
  position: relative;
}
.inner{
  height: 100%;
  overflow: scroll;
}
.full-height{
  position: absolute;
  left: 0;
  width: 20%;
  top: 0;
  height: 100%;
}

'this' is undefined in JavaScript class methods

I just wanted to point out that sometimes this error happens because a function has been used as a high order function (passed as an argument) and then the scope of this got lost. In such cases, I would recommend passing such function bound to this. E.g.

this.myFunction.bind(this);

Make <body> fill entire screen?

html, body {
    margin: 0;
    height: 100%;
}

ERROR Error: No value accessor for form control with unspecified name attribute on switch

I also received this error while writing a custom form control component in Angular 7. However, none of the answers are applicable to Angular 7.

In my case, the following needed to be add to the @Component decorator:

  providers: [
    {
      provide: NG_VALUE_ACCESSOR,
      useExisting: forwardRef(() => MyCustomComponent),  // replace name as appropriate
      multi: true
    }
  ]

This is a case of "I don't know why it works, but it does." Chalk it up to poor design/implementation on the part of Angular.

What is the difference between "INNER JOIN" and "OUTER JOIN"?

The precise algorithm for INNER JOIN, LEFT/RIGHT OUTER JOIN are as following:

  1. Take each row from the first table: a
  2. Consider all rows from second table beside it: (a, b[i])
  3. Evaluate the ON ... clause against each pair: ON( a, b[i] ) = true/false?
    • When the condition evaluates to true, return that combined row (a, b[i]).
    • When reach end of second table without any match, and this is an Outer Join then return a (virtual) pair using Null for all columns of other table: (a, Null) for LEFT outer join or (Null, b) for RIGHT outer join. This is to ensure all rows of first table exists in final results.

Note: the condition specified in ON clause could be anything, it is not required to use Primary Keys (and you don't need to always refer to Columns from both tables)! For example:

Inner Join vs. Left Outer Join


enter image description here

Note: Left Join = Left Outer Join, Right Join = Right Outer Join.

JPA COUNT with composite primary key query not working

Use count(d.ertek) or count(d.id) instead of count(d). This can be happen when you have composite primary key at your entity.

Measuring elapsed time with the Time module

Here is an update to Vadim Shender's clever code with tabular output:

import collections
import time
from functools import wraps

PROF_DATA = collections.defaultdict(list)

def profile(fn):
    @wraps(fn)
    def with_profiling(*args, **kwargs):
        start_time = time.time()
        ret = fn(*args, **kwargs)
        elapsed_time = time.time() - start_time
        PROF_DATA[fn.__name__].append(elapsed_time)
        return ret
    return with_profiling

Metrics = collections.namedtuple("Metrics", "sum_time num_calls min_time max_time avg_time fname")

def print_profile_data():
    results = []
    for fname, elapsed_times in PROF_DATA.items():
        num_calls = len(elapsed_times)
        min_time = min(elapsed_times)
        max_time = max(elapsed_times)
        sum_time = sum(elapsed_times)
        avg_time = sum_time / num_calls
        metrics = Metrics(sum_time, num_calls, min_time, max_time, avg_time, fname)
        results.append(metrics)
    total_time = sum([m.sum_time for m in results])
    print("\t".join(["Percent", "Sum", "Calls", "Min", "Max", "Mean", "Function"]))
    for m in sorted(results, reverse=True):
        print("%.1f\t%.3f\t%d\t%.3f\t%.3f\t%.3f\t%s" % (100 * m.sum_time / total_time, m.sum_time, m.num_calls, m.min_time, m.max_time, m.avg_time, m.fname))
    print("%.3f Total Time" % total_time)

How to query as GROUP BY in django?

The following module allows you to group Django models and still work with a QuerySet in the result: https://github.com/kako-nawao/django-group-by

For example:

from django_group_by import GroupByMixin

class BookQuerySet(QuerySet, GroupByMixin):
    pass

class Book(Model):
    title = TextField(...)
    author = ForeignKey(User, ...)
    shop = ForeignKey(Shop, ...)
    price = DecimalField(...)

class GroupedBookListView(PaginationMixin, ListView):
    template_name = 'book/books.html'
    model = Book
    paginate_by = 100

    def get_queryset(self):
        return Book.objects.group_by('title', 'author').annotate(
            shop_count=Count('shop'), price_avg=Avg('price')).order_by(
            'name', 'author').distinct()

    def get_context_data(self, **kwargs):
        return super().get_context_data(total_count=self.get_queryset().count(), **kwargs)

'book/books.html'

<ul>
{% for book in object_list %}
    <li>
        <h2>{{ book.title }}</td>
        <p>{{ book.author.last_name }}, {{ book.author.first_name }}</p>
        <p>{{ book.shop_count }}</p>
        <p>{{ book.price_avg }}</p>
    </li>
{% endfor %}
</ul>

The difference to the annotate/aggregate basic Django queries is the use of the attributes of a related field, e.g. book.author.last_name.

If you need the PKs of the instances that have been grouped together, add the following annotation:

.annotate(pks=ArrayAgg('id'))

NOTE: ArrayAgg is a Postgres specific function, available from Django 1.9 onwards: https://docs.djangoproject.com/en/1.10/ref/contrib/postgres/aggregates/#arrayagg

fatal: could not read Username for 'https://github.com': No such file or directory

I fixed this by installing a newer version of Git. The version I installed is 2.10.2 from https://git-scm.com. See the last post here: https://www.bountysource.com/issues/31602800-git-fails-to-authenticate-access-to-private-repository-over-https

With newer Git Bash, the credential manager window pops up and you can enter your username and password, and it works!

View the change history of a file using Git versioning

With the excellent Git Extensions, you go to a point in the history where the file still existed (if it have been deleted, otherwise just go to HEAD), switch to the File tree tab, right-click on the file and choose File history.

By default, it follows the file through the renames, and the Blame tab allows to see the name at a given revision.

It has some minor gotchas, like showing fatal: Not a valid object name in the View tab when clicking on the deletion revision, but I can live with that. :-)

How to set the 'selected option' of a select dropdown list with jquery

Set the value it will set it as selected option for dropdown:

$("#salesrep").val("Bruce Jones");

Here is working Demo

If it still not working:

  1. Please check JavaScript errors on console.
  2. Make sure you included jquery files
  3. your network is not blocking jquery file if using externally.
  4. Check your view source some time exact copy of element stop jquery to work correctly

Hadoop MapReduce: Strange Result when Storing Previous Value in Memory in a Reduce Class (Java)

It is very inefficient to store all values in memory, so the objects are reused and loaded one at a time. See this other SO question for a good explanation. Summary:

[...] when looping through the Iterable value list, each Object instance is re-used, so it only keeps one instance around at a given time.

How to add header data in XMLHttpRequest when using formdata?

Use: xmlhttp.setRequestHeader(key, value);

How to change the timeout on a .NET WebClient object

The first solution did not work for me but here is some code that did work for me.

    private class WebClient : System.Net.WebClient
    {
        public int Timeout { get; set; }

        protected override WebRequest GetWebRequest(Uri uri)
        {
            WebRequest lWebRequest = base.GetWebRequest(uri);
            lWebRequest.Timeout = Timeout;
            ((HttpWebRequest)lWebRequest).ReadWriteTimeout = Timeout;
            return lWebRequest;
        }
    }

    private string GetRequest(string aURL)
    {
        using (var lWebClient = new WebClient())
        {
            lWebClient.Timeout = 600 * 60 * 1000;
            return lWebClient.DownloadString(aURL);
        }
    }

how to add key value pair in the JSON object already declared

Hi I add key and value to each object

_x000D_
_x000D_
let persons = [_x000D_
  {_x000D_
    name : "John Doe Sr",_x000D_
    age: 30_x000D_
  },{_x000D_
    name: "John Doe Jr",_x000D_
    age : 5_x000D_
  }_x000D_
]_x000D_
_x000D_
function addKeyValue(obj, key, data){_x000D_
  obj[key] = data;_x000D_
}_x000D_
 _x000D_
_x000D_
let newinfo = persons.map(function(person) {_x000D_
  return addKeyValue(person, 'newKey', 'newValue');_x000D_
});_x000D_
_x000D_
console.log(persons);
_x000D_
_x000D_
_x000D_

onclick open window and specific size

Using function in typescript

openWindow(){
    //you may choose to deduct some value from current screen size
    let height = window.screen.availHeight-100;
    let width = window.screen.availWidth-150;
    window.open("http://your_url",`width=${width},height=${height}`);
}

How to see the CREATE VIEW code for a view in PostgreSQL?

select pg_get_viewdef('viewname', true)

A list of all those functions is available in the manual:

http://www.postgresql.org/docs/current/static/functions-info.html

How to embed images in html email

This is the code I'm using to embed images into HTML mail and PDF documents.

<?php
$logo_path = 'http://localhost/img/logo.jpg';
$type = pathinfo($logo_path, PATHINFO_EXTENSION);
$image_contents = file_get_contents($logo_path);
$image64 = 'data:image/' . $type . ';base64,' . base64_encode($image_contents);

echo '<img src="' . $image64 .'" />';
?>

Delete all files of specific type (extension) recursively down a directory using a batch file

I don't have enough reputation to add comment, so I posted this as an answer. But for original issue with this command:

@echo off
FOR %%p IN (C:\Users\vexe\Pictures\sample) DO FOR %%t IN (*.jpg) DO del /s %%p\%%t

The first For is lacking recursive syntax, it should be:

@echo off
FOR /R %%p IN (C:\Users\vexe\Pictures\sample) DO FOR %%t IN (*.jpg) DO del /s %%p\%%t

You can just do:

FOR %%p IN (C:\Users\0300092544\Downloads\Ces_Sce_600) DO @ECHO %%p

to show the actual output.

How to deploy a React App on Apache web server

Before making the npm build,
1) Go to your React project root folder and open package.json.
2) Add "homepage" attribute to package.json

  • if you want to provide absolute path

    "homepage": "http://hostName.com/appLocation",
    "name": "react-app",
    "version": "1.1.0",
    
  • if you want to provide relative path

    "homepage": "./",
    "name": "react-app",
    

    Using relative path method may warn a syntax validation error in your IDE. But the build is made without any errors during compilation.

3) Save the package.json , and in terminal run npm run-script build
4) Copy the contents of build/ folder to your server directory.

PS: It is easy to use relative path method if you want to change the build file location in your server frequently.

Calculating Page Table Size

Since we have a virtual address space of 2^32 and each page size is 2^12, we can store (2^32/2^12) = 2^20 pages. Since each entry into this page table has an address of size 4 bytes, then we have 2^20*4 = 4MB. So the page table takes up 4MB in memory.

Using Vim's tabs like buffers

Stop, stop, stop.

This is not how Vim's tabs are designed to be used. In fact, they're misnamed. A better name would be "viewport" or "layout", because that's what a tab is—it's a different layout of windows of all of your existing buffers.

Trying to beat Vim into 1 tab == 1 buffer is an exercise in futility. Vim doesn't know or care and it will not respect it on all commands—in particular, anything that uses the quickfix buffer (:make, :grep, and :helpgrep are the ones that spring to mind) will happily ignore tabs and there's nothing you can do to stop that.

Instead:

  • :set hidden
    If you don't have this set already, then do so. It makes vim work like every other multiple-file editor on the planet. You can have edited buffers that aren't visible in a window somewhere.
  • Use :bn, :bp, :b #, :b name, and ctrl-6 to switch between buffers. I like ctrl-6 myself (alone it switches to the previously used buffer, or #ctrl-6 switches to buffer number #).
  • Use :ls to list buffers, or a plugin like MiniBufExpl or BufExplorer.

Read text from response

The accepted answer does not correctly dispose the WebResponse or decode the text. Also, there's a new way to do this in .NET 4.5.

To perform an HTTP GET and read the response text, do the following.

.NET 1.1 - 4.0

public static string GetResponseText(string address)
{
    var request = (HttpWebRequest)WebRequest.Create(address);

    using (var response = (HttpWebResponse)request.GetResponse())
    {
        var encoding = Encoding.GetEncoding(response.CharacterSet);

        using (var responseStream = response.GetResponseStream())
        using (var reader = new StreamReader(responseStream, encoding))
            return reader.ReadToEnd();
    }
}

.NET 4.5

private static readonly HttpClient httpClient = new HttpClient();

public static async Task<string> GetResponseText(string address)
{
    return await httpClient.GetStringAsync(address);
}

How to set image to UIImage

just change this line

[img setImage:[UIImage imageNamed:@"anyImageName"]];

with following line

img = [UIImage imageNamed:@"anyImageName"];

Get size of all tables in database

After some searching, I could not find an easy way to get information on all of the tables. There is a handy stored procedure named sp_spaceused that will return all of the space used by the database. If provided with a table name, it returns the space used by that table. However, the results returned by the stored procedure are not sortable, since the columns are character values.

The following script will generate the information I'm looking for.

create table #TableSize (
    Name varchar(255),
    [rows] int,
    reserved varchar(255),
    data varchar(255),
    index_size varchar(255),
    unused varchar(255))
create table #ConvertedSizes (
    Name varchar(255),
    [rows] int,
    reservedKb int,
    dataKb int,
    reservedIndexSize int,
    reservedUnused int)

EXEC sp_MSforeachtable @command1="insert into #TableSize
EXEC sp_spaceused '?'"
insert into #ConvertedSizes (Name, [rows], reservedKb, dataKb, reservedIndexSize, reservedUnused)
select name, [rows], 
SUBSTRING(reserved, 0, LEN(reserved)-2), 
SUBSTRING(data, 0, LEN(data)-2), 
SUBSTRING(index_size, 0, LEN(index_size)-2), 
SUBSTRING(unused, 0, LEN(unused)-2)
from #TableSize

select * from #ConvertedSizes
order by reservedKb desc

drop table #TableSize
drop table #ConvertedSizes

Microsoft Web API: How do you do a Server.MapPath?

Since Server.MapPath() does not exist within a Web Api (Soap or REST), you'll need to denote the local- relative to the web server's context- home directory. The easiest way to do so is with:

string AppContext.BaseDirectory { get;}

You can then use this to concatenate a path string to map the relative path to any file.
NOTE: string paths are \ and not / like they are in mvc.

Ex:

System.IO.File.Exists($"{**AppContext.BaseDirectory**}\\\\Content\\\\pics\\\\{filename}");

returns true- positing that this is a sound path in your example

Android 1.6: "android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application"

As it's said, you need an Activity as context for the dialog, use "YourActivity.this" for a static context or check here for how to use a dynamic one in a safe mode

Logical operator in a handlebars.js {{#if}} conditional

Similar to Jim's answer but a using a bit of creativity we could also do something like this:

Handlebars.registerHelper( "compare", function( v1, op, v2, options ) {

  var c = {
    "eq": function( v1, v2 ) {
      return v1 == v2;
    },
    "neq": function( v1, v2 ) {
      return v1 != v2;
    },
    ...
  }

  if( Object.prototype.hasOwnProperty.call( c, op ) ) {
    return c[ op ].call( this, v1, v2 ) ? options.fn( this ) : options.inverse( this );
  }
  return options.inverse( this );
} );

Then to use it we get something like:

{{#compare numberone "eq" numbretwo}}
  do something
{{else}}
  do something else
{{/compare}}

I would suggest moving the object out of the function for better performance but otherwise you can add any compare function you want, including "and" and "or".

use of entityManager.createNativeQuery(query,foo.class)

That doesn't work because the second parameter should be a mapped entity and of course Integer is not a persistent class (since it doesn't have the @Entity annotation on it).

for you you should do the following:

Query q = em.createNativeQuery("select id from users where username = :username");
q.setParameter("username", "lt");
List<BigDecimal> values = q.getResultList();

or if you want to use HQL you can do something like this:

Query q = em.createQuery("select new Integer(id) from users where username = :username");
q.setParameter("username", "lt");
List<Integer> values = q.getResultList();

Regards.

CSS media query to target only iOS devices

Short answer No. CSS is not specific to brands.

Below are the articles to implement for iOS using media only.

https://css-tricks.com/snippets/css/media-queries-for-standard-devices/

http://stephen.io/mediaqueries/

Infact you can use PHP, Javascript to detect the iOS browser and according to that you can call CSS file. For instance

http://www.kevinleary.net/php-detect-ios-mobile-users/

How to quickly edit values in table in SQL Server Management Studio?

In Mgmt Studio, when you are editing the top 200, you can view the SQL pane - either by right clicking in the grid and choosing Pane->SQL or by the button in the upper left. This will allow you to write a custom query to drill down to the row(s) you want to edit.

But ultimately mgmt studio isn't a data entry/update tool which is why this is a little cumbersome.

Confirm Password with jQuery Validate

jQuery('.validatedForm').validate({
        rules : {
            password : {
                minlength : 5
            },
            password_confirm : {
                minlength : 5,
                equalTo : '[name="password"]'
            }
        }

In general, you will not use id="password" like this. So, you can use [name="password"] instead of "#password"

How can I show an element that has display: none in a CSS rule?

document.getElementById('mybox').style.display = "block";

Bootstrap full-width text-input within inline-form

Try something like below to achieve your desired result

input {
    max-width: 100%;
}

Where is the WPF Numeric UpDown control?

This is example of my own UserControl with Up and Down key catching.

Xaml code:

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="13" />
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="13" />
        <RowDefinition Height="13" />
    </Grid.RowDefinitions>
    <TextBox Name="NUDTextBox"  Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" TextAlignment="Right" PreviewKeyDown="NUDTextBox_PreviewKeyDown" PreviewKeyUp="NUDTextBox_PreviewKeyUp" TextChanged="NUDTextBox_TextChanged"/>
    <RepeatButton Name="NUDButtonUP"  Grid.Column="1" Grid.Row="0" FontSize="8" FontFamily="Marlett" VerticalContentAlignment="Center" HorizontalContentAlignment="Center" Click="NUDButtonUP_Click">5</RepeatButton>
    <RepeatButton Name="NUDButtonDown"  Grid.Column="1" Grid.Row="1" FontSize="8"  FontFamily="Marlett" VerticalContentAlignment="Center" HorizontalContentAlignment="Center" Height="13" VerticalAlignment="Bottom" Click="NUDButtonDown_Click">6</RepeatButton>
</Grid>

And the code:

public partial class NumericUpDown : UserControl
{
    int minvalue = 0, 
        maxvalue = 100,
        startvalue = 10;
    public NumericUpDown()
    {
        InitializeComponent();
        NUDTextBox.Text = startvalue.ToString();
    }

    private void NUDButtonUP_Click(object sender, RoutedEventArgs e)
    {
        int number;
        if (NUDTextBox.Text != "") number = Convert.ToInt32(NUDTextBox.Text);
        else number = 0;
        if (number < maxvalue)
            NUDTextBox.Text = Convert.ToString(number + 1); 
    }

    private void NUDButtonDown_Click(object sender, RoutedEventArgs e)
    {
        int number;
        if (NUDTextBox.Text != "") number = Convert.ToInt32(NUDTextBox.Text);
        else number = 0;
        if (number > minvalue)
            NUDTextBox.Text = Convert.ToString(number - 1); 
    }

    private void NUDTextBox_PreviewKeyDown(object sender, KeyEventArgs e)
    {

        if (e.Key == Key.Up)
        {
            NUDButtonUP.RaiseEvent(new RoutedEventArgs(Button.ClickEvent));
            typeof(Button).GetMethod("set_IsPressed", BindingFlags.Instance | BindingFlags.NonPublic).Invoke(NUDButtonUP, new object[] { true }); 
        }


        if (e.Key == Key.Down)
        {
            NUDButtonDown.RaiseEvent(new RoutedEventArgs(Button.ClickEvent));
            typeof(Button).GetMethod("set_IsPressed", BindingFlags.Instance | BindingFlags.NonPublic).Invoke(NUDButtonDown, new object[] { true }); 
        }
    }

    private void NUDTextBox_PreviewKeyUp(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Up)
            typeof(Button).GetMethod("set_IsPressed", BindingFlags.Instance | BindingFlags.NonPublic).Invoke(NUDButtonUP, new object[] { false });

        if (e.Key == Key.Down)
            typeof(Button).GetMethod("set_IsPressed", BindingFlags.Instance | BindingFlags.NonPublic).Invoke(NUDButtonDown, new object[] { false });
    }

    private void NUDTextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        int number = 0;
        if (NUDTextBox.Text!="")
            if (!int.TryParse(NUDTextBox.Text, out number)) NUDTextBox.Text = startvalue.ToString();
        if (number > maxvalue)  NUDTextBox.Text = maxvalue.ToString();
        if (number < minvalue) NUDTextBox.Text = minvalue.ToString();
        NUDTextBox.SelectionStart = NUDTextBox.Text.Length;

    }

}

Laravel 5: Display HTML with Blade

I have been there and it was my fault. And very stupid one.

if you forget .blade extension in the file name, that file doesn't understand blade but runs php code. You should use

/resources/views/filename.blade.php

instead of

/resources/views/filename.php

hope this helps some one

Today's Date in Perl in MM/DD/YYYY format

You can do it fast, only using one POSIX function. If you have bunch of tasks with dates, see the module DateTime.

use POSIX qw(strftime);

my $date = strftime "%m/%d/%Y", localtime;
print $date;

What is the difference between concurrency and parallelism?

Concurrency is when two or more tasks can start, run, and complete in overlapping time periods. It doesn't necessarily mean they'll ever both be running at the same instant. For example, multitasking on a single-core machine.

Parallelism is when tasks literally run at the same time, e.g., on a multicore processor.


Quoting Sun's Multithreaded Programming Guide:

  • Concurrency: A condition that exists when at least two threads are making progress. A more generalized form of parallelism that can include time-slicing as a form of virtual parallelism.

  • Parallelism: A condition that arises when at least two threads are executing simultaneously.

Regex to match words of a certain length

I think you want \b\w{1,10}\b. The \b matches a word boundary.

Of course, you could also replace the \b and do ^\w{1,10}$. This will match a word of at most 10 characters as long as its the only contents of the string. I think this is what you were doing before.

Since it's Java, you'll actually have to escape the backslashes: "\\b\\w{1,10}\\b". You probably knew this already, but it's gotten me before.

What is the total amount of public IPv4 addresses?

https://www.ripe.net/internet-coordination/press-centre/understanding-ip-addressing

For IPv4, this pool is 32-bits (2³²) in size and contains 4,294,967,296 IPv4 addresses.

In case of IPv6

The IPv6 address space is 128-bits (2¹²8) in size, containing 340,282,366,920,938,463,463,374,607,431,768,211,456 IPv6 addresses.

inclusive of RESERVED IP

 Reserved address blocks
 Range  Description Reference

 0.0.0.0/8  Current network (only valid as source address)  RFC 6890
 10.0.0.0/8 Private network RFC 1918
 100.64.0.0/10  Shared Address Space    RFC 6598
 127.0.0.0/8    Loopback    RFC 6890
 169.254.0.0/16 Link-local  RFC 3927
 172.16.0.0/12  Private network RFC 1918
 192.0.0.0/24   IETF Protocol Assignments   RFC 6890
 192.0.2.0/24   TEST-NET-1, documentation and examples  RFC 5737
 192.88.99.0/24 IPv6 to IPv4 relay (includes 2002::/16) RFC 3068
 192.168.0.0/16 Private network RFC 1918
 198.18.0.0/15  Network benchmark tests RFC 2544
 198.51.100.0/24    TEST-NET-2, documentation and examples  RFC 5737
 203.0.113.0/24 TEST-NET-3, documentation and examples  RFC 5737
 224.0.0.0/4    IP multicast (former Class D network)   RFC 5771
 240.0.0.0/4    Reserved (former Class E network)   RFC 1700
 255.255.255.255    Broadcast   RFC 919

wiki has full details and this has details of IPv6.

R color scatter plot points based on values

It's better to create a new factor variable using cut(). I've added a few options using ggplot2 also.

df <- data.frame(
  X1=seq(0, 5, by=0.001),
  X2=rnorm(df$X1, mean = 3.5, sd = 1.5)
)

# Create new variable for plotting
df$Colour <- cut(df$X2, breaks = c(-Inf, 1, 3, +Inf), 
                 labels = c("low", "medium", "high"), 
                 right = FALSE)

### Base Graphics

plot(df$X1, df$X2, 
     col = df$Colour, ylim = c(0, 10), xlab = "POS", 
     ylab = "CS", main = "Plot Title", pch = 21)

plot(df$X1,df$X2, 
     col = df$Colour, ylim = c(0, 10), xlab = "POS", 
     ylab = "CS", main = "Plot Title", pch = 19, cex = 0.5)

# Using `with()` 

with(df, 
     plot(X1, X2, xlab="POS", ylab="CS", col = Colour, pch=21, cex=1.4)
     )

# Using ggplot2
library(ggplot2)

# qplot()
qplot(df$X1, df$X2, colour = df$Colour)

# ggplot()
p <- ggplot(df, aes(X1, X2, colour = Colour)) 
p <- p + geom_point() + xlab("POS") + ylab("CS")
p

p + facet_grid(Colour~., scales = "free")

Overloading and overriding

Another point to add.

Overloading More than one method with Same name. Same or different return type. Different no of parameters or Different type of parameters. In Same Class or Derived class.

int Add(int num1, int num2) int Add(int num1, int num2, int num3) double Add(int num1, int num2) double Add(double num1, double num2)

Can be possible in same class or derived class. Generally prefers in same class. E.g. Console.WriteLine() has 19 overloaded methods.

Can overload class constructors, methods.

Can consider as Compile Time (static / Early Binding) polymorphism.

=====================================================================================================

Overriding cannot be possible in same class. Can Override class methods, properties, indexers, events.

Has some limitations like The overridden base method must be virtual, abstract, or override. You cannot use the new, static, or virtual modifiers to modify an override method.

Can Consider as Run Time (Dynamic / Late Binding) polymorphism.

Helps in versioning http://msdn.microsoft.com/en-us/library/6fawty39.aspx

=====================================================================================================

Helpful Links

http://msdn.microsoft.com/en-us/library/ms173152.aspx Compile time polymorphism vs. run time polymorphism

Case-insensitive string comparison in C++

I wrote a case-insensitive version of char_traits for use with std::basic_string in order to generate a std::string that is not case-sensitive when doing comparisons, searches, etc using the built-in std::basic_string member functions.

So in other words, I wanted to do something like this.

std::string a = "Hello, World!";
std::string b = "hello, world!";

assert( a == b );

...which std::string can't handle. Here's the usage of my new char_traits:

std::istring a = "Hello, World!";
std::istring b = "hello, world!";

assert( a == b );

...and here's the implementation:

/*  ---

        Case-Insensitive char_traits for std::string's

        Use:

            To declare a std::string which preserves case but ignores case in comparisons & search,
            use the following syntax:

                std::basic_string<char, char_traits_nocase<char> > noCaseString;

            A typedef is declared below which simplifies this use for chars:

                typedef std::basic_string<char, char_traits_nocase<char> > istring;

    --- */

    template<class C>
    struct char_traits_nocase : public std::char_traits<C>
    {
        static bool eq( const C& c1, const C& c2 )
        { 
            return ::toupper(c1) == ::toupper(c2); 
        }

        static bool lt( const C& c1, const C& c2 )
        { 
            return ::toupper(c1) < ::toupper(c2);
        }

        static int compare( const C* s1, const C* s2, size_t N )
        {
            return _strnicmp(s1, s2, N);
        }

        static const char* find( const C* s, size_t N, const C& a )
        {
            for( size_t i=0 ; i<N ; ++i )
            {
                if( ::toupper(s[i]) == ::toupper(a) ) 
                    return s+i ;
            }
            return 0 ;
        }

        static bool eq_int_type( const int_type& c1, const int_type& c2 )
        { 
            return ::toupper(c1) == ::toupper(c2) ; 
        }       
    };

    template<>
    struct char_traits_nocase<wchar_t> : public std::char_traits<wchar_t>
    {
        static bool eq( const wchar_t& c1, const wchar_t& c2 )
        { 
            return ::towupper(c1) == ::towupper(c2); 
        }

        static bool lt( const wchar_t& c1, const wchar_t& c2 )
        { 
            return ::towupper(c1) < ::towupper(c2);
        }

        static int compare( const wchar_t* s1, const wchar_t* s2, size_t N )
        {
            return _wcsnicmp(s1, s2, N);
        }

        static const wchar_t* find( const wchar_t* s, size_t N, const wchar_t& a )
        {
            for( size_t i=0 ; i<N ; ++i )
            {
                if( ::towupper(s[i]) == ::towupper(a) ) 
                    return s+i ;
            }
            return 0 ;
        }

        static bool eq_int_type( const int_type& c1, const int_type& c2 )
        { 
            return ::towupper(c1) == ::towupper(c2) ; 
        }       
    };

    typedef std::basic_string<char, char_traits_nocase<char> > istring;
    typedef std::basic_string<wchar_t, char_traits_nocase<wchar_t> > iwstring;

ValueError: unsupported format character while forming strings

Well, why do you have %20 url-quoting escapes in a formatting string in first place? Ideally you'd do the interpolation formatting first:

formatting_template = 'Hello World%s'
text = '!'
full_string = formatting_template % text

Then you url quote it afterwards:

result = urllib.quote(full_string)

That is better because it would quote all url-quotable things in your string, including stuff that is in the text part.

Which Radio button in the group is checked?

if you want to save the selection to file or any else and call it later, here what I do

string[] lines = new string[1];

lines[0]  = groupBoxTes.Controls.OfType<RadioButton>()
            .FirstOrDefault(r => r.Checked).Text;

File.WriteAllLines("Config.ini", lines);

then call it with

string[] ini = File.ReadAllLines("Config.ini");
groupBoxTes.Controls.OfType<RadioButton>()
.FirstOrDefault(r => (r.Text == ini[0])).Checked = true;

Passing by reference in C

Because you're passing the value of the pointer to the method and then dereferencing it to get the integer that is pointed to.

Get individual query parameters from Uri

This should work:

string url = "http://example.com/file?a=1&b=2&c=string%20param";
string querystring = url.Substring(url.IndexOf('?'));
System.Collections.Specialized.NameValueCollection parameters = 
   System.Web.HttpUtility.ParseQueryString(querystring);

According to MSDN. Not the exact collectiontype you are looking for, but nevertheless useful.

Edit: Apparently, if you supply the complete url to ParseQueryString it will add 'http://example.com/file?a' as the first key of the collection. Since that is probably not what you want, I added the substring to get only the relevant part of the url.

SSL certificate is not trusted - on mobile only

The most likely reason for the error is that the certificate authority that issued your SSL certificate is trusted on your desktop, but not on your mobile.

If you purchased the certificate from a common certification authority, it shouldn't be an issue - but if it is a less common one it is possible that your phone doesn't have it. You may need to accept it as a trusted publisher (although this is not ideal if you are pushing the site to the public as they won't be willing to do this.)

You might find looking at a list of Trusted CAs for Android helps to see if yours is there or not.

Android Paint: .measureText() vs .getTextBounds()

There is another way to measure the text bounds precisely, first you should get the path for the current Paint and text. In your case it should be like this:

p.getTextPath(someText, 0, someText.length(), 0.0f, 0.0f, mPath);

After that you can call:

mPath.computeBounds(mBoundsPath, true);

In my code it always returns correct and expected values. But, not sure if it works faster than your approach.