What is JSON and why would I use it

Question

I ve looked on wikipedia and Googled it and read the official documentation  but I still haven t got to the point where I really understand what JSON is  and why I d use it    I have been building applications using PHP  MySQL and Javascript   HTML for a while  and if JSON can do something to make my life easier or my code better or my user interface better  then I d like to know about it  Can someone give me a succinct explanation

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The JSON format is often used for serializing and transmitting structured data over a network connection  It is used primarily to transmit data between a server and web application  serving as an alternative to XML

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The difference between JSON and conventional syntax would be as follows  in Javascript   Conventional   function Employee name  Id  Phone  email          this name   name        this Id   Id        this Phone   Phone        this email   email           access or call it as   var Emp   new Employee  mike   123   9373849784   mike Anderson office com      With JSON   if we use JSON we can define in different way as    function Employee args       this name   args name     this Id   args Id     this Phone   args Phone     this email   args email       now access this as     var Emp   new Employee   name   Mike    Id   123    Phone   23792747    email   mike adnersone office com       The important thing we have to remember is that   if we have to build the  Employee  class or modal with 100 elements without JSON method we have to parse everything when creating class  But with JSON we can define the objects inline only when a new object for the class is defined   so this line below is the way of doing things with JSON just a simple way to define things    var Emp   new Employee   name   Mike    Id   123    Phone   23792747    email   mike adnersone office com

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Sometimes technicality is given where none is required  and while many of the top voted answers are accurately technical and specific  I personally don t think they are any more easy to understand  or succinct  as what can be found on Wikipedia  or in official documentation   The way I like to think of JSON is exactly what it is - a language within a world of different languages  However  the difference between JSON and other languages is that  everyone   speaks  JSON  along with their  native language    Using a real world example  let s pretend we have three people  One person speaks Igbo as their native tongue  The second person would like to interact with the first person  however  the first person speaks Yoruba as their first language   What can we do   Thankfully  the third person in our example grew up speaking English  but also happens to speak both Igbo and Yoruba as second languages  and so can act as an intermediary between the first two individuals   In the programming world  the first  person  is Python  the second  person  is Ruby  and the third  person  is JSON  who just so happens to be able to  translate  Ruby into Python and vice versa  Now obviously this analogy isn t a perfect one  but  as someone who is bilingual  I believe it s an easy way to look at how JSON interacts with other programming languages

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The Concept Explained - No Code or Technical Jargon What is JSON      How I explained it to my wifeTM Me     It   s basically a way of communicating with someone in writing    but with very specific rules  Wife  yeah      Me  In prosaic English  the rules are pretty loose  just like with cage fighting  Not so with JSON  There are many ways of describing something        Example 1  Our family has 4 people  You  me and 2 kids        Example 2  Our family  you  me  kid1 and kid2        Example 3  Family    you  me  kid1  kid2        Example 4  we got 4 people in our family  mum  dad  kid1 and kid2  Wife  Why don   t they just use plain English instead  Me  They would  but remember we   re dealing with computers  A computer is stupid and is not going to be able to understand sentences  So we gotta be really specific when computers are involved otherwise they get confused  Furthermore  JSON is a fairly efficient way of communicating  so most of the irrelevant stuff is cut out  which is pretty hand  If you wanted to communicate our family  to a computer  one way you could do so is like this         quot Family quot     quot Me quot    quot Wife quot    quot Kid1 quot    quot Kid2 quot             and that is basically JSON  But remember  you MUST obey the JSON grammar rules  If you break those rules  then a computer simply will not understand  i e  parse  what you are writing  Wife  So how do I write in Json  A good way would be to use a json serialiser - which is a library which does the heavy lifting for you  Summary  JSON is basically a way of communicating data to someone  with very  very specific rules  Using Key Value Pairs and Arrays  This is the concept explained  at this point it is worth reading the specific rules above

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I like JSON mainly because it s so terse   For web content that can be gzipped  this isn t necessarily a big deal  hence why xhtml is so popular    But there are occasions where  this can be beneficial   For example  for one project I was transmitting information that needed to be serialized and transmitted via XMPP   Since most servers will limit the amount of data you can transmit in a single message  I found it helpful to use JSON over the obvious alternative  XML   As an added bonus  if you re familiar with Python or Javascript  you already pretty much know JSON and can interpret it without much training at all

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Understanding JSON JSON is just a text format that most REST APIs use to return their data  Another common format is XML  but XML is quite a bit more verbose  Here   s a small example of JSON     JSON object      quot name quot    quot John quot      quot age quot   20       JSON array            quot name quot    quot John quot        quot age quot   20               quot name quot    quot Peter quot        quot age quot   22        Notice that the snippet starts with a brace    which indicates an object  JSON can also start as an array  which uses the square bracket   symbol to signify the start of the array  JSON needs to be properly formatted  so all beginning   and   symbols need to have their ending symbols    and    JSON can contain object or array  An object in JSON is wrapped inside the braces          while an array is wrapped inside square brackets          JSON structures data by key-value  Key is always a string  but value could be anything  String  number  JSON object  JSON array      This will affect the way we parse JSON in the next steps

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the common short answer is  if you are using AJAX to make data requests  you can easily send and return objects as JSON strings  Available extensions for Javascript support toJSON   calls on all javascript types for sending data to the server in an AJAX request  AJAX responses can return objects as JSON strings which can be converted into Javascript objects by a simple eval call  e g  if the AJAX function someAjaxFunctionCallReturningJson returned        FirstName       Fred      LastName       Flintstone        you could write in Javascript  var obj   eval       someAjaxFunctionCallReturningJson   value         alert obj FirstName   alert obj LastName     JSON can also be used for web service payloads et al  but it is really convenient for AJAX results    Update  ten years later   Don t do this  use JSON parse

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Try the following code to parse your php json response  read php   lt script   src  https   code jquery com jquery-3 2 1 min js    integrity  sha256-hwg4gsxgFZhOsEEamdOYGBf13FyQuiTwlAQgxVSNgt4     crossorigin  anonymous  gt  lt  script gt   lt script type  text javascript  gt      ajax       url  index php       data         type  POST       success function result            jsondecoded     parseJSON result             each jsondecoded  function index  value                    servers   text     servers   text           value servername               console log value start               console log value end               console log value id                          statusCode        404  function           alert   page not found                    lt  script gt    server php   lt  php  echo     start   2017-08-29   end   2017-09-01   id   22     start   2017-09-03   end   2017-09-06   id   23        gt

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We have to do a project on college and we faced a very big problem  it is called Same Origin Policy  Amog other things  it makes that your XMLHttpRequest method from Javascript can t make requests to domains other than the domain that your site is on    For example you can t make request to www otherexample com if your site is on www example com  JSONRequest allows that  but you will get result in JSON format if that site allows that for example it has a web service that returns messages in JSON   That is one problem where you could use JSON perhaps   Here is something practical  Yahoo JSON

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In the Java context  one reason why JSON might want to be used  is that it provides a very good alternative to Java s Serialization framework  which has been shown  historically  to be subject to some fairly serious vulnerabilities    Joshua Bloch discusses this in depth in Item 85  Prefer Alternatives to Java Serialization   Effective Java 3rd Edition   Java s Serialization was initially meant to translate data structures into a format that could be easily transmitted or stored  JSON meets this requirement  without the serious exploits referred to above

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JSON Javascript object notation  is a light weight data format for data exchange transfer  Its in key value pair as the JavaScript is  For REST API its widely used for data transfer from server to client  Nowadays many of the social media sites are using this  Although I don t see this as robust as XML with respect of data types  XML has very rich datatypes and XSD  JSON is bit lacking in this   For same amount of string data JSON will be lighter compare to XML as XML has all that opening and closing tags  etc

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JSON is JavaScript Object Notation  It is a much-more compact way of transmitting sets of data across network connections as compared to XML  I suggest JSON be used in any AJAX-like applications where XML would otherwise be the  recommended  option  The verbosity of XML will add to download time and increased bandwidth consumption        You can accomplish the same effect with JSON and its mark-up is almost exclusively dedicated to the data itself and not the underlying structure

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JSON  JavaScript Object Notation  is a lightweight format that is used for data interchanging   It is based on a subset of JavaScript language  the way objects are built in JavaScript   As stated in the MDN  some JavaScript is not JSON  and some JSON is not JavaScript   An example of  where this is used is web services responses   In the  old  days  web services used XML as their primary data format for transmitting back data  but since JSON appeared  The JSON format is specified in RFC 4627 by Douglas Crockford   it has been the preferred format because it is much more lightweight  You can find a lot more info on the official JSON web site   JSON is built on two structures    A collection of name value pairs  In various languages  this is realized as an object  record  struct  dictionary  hash table  keyed list  or associative array  An ordered list of values  In most languages  this is realized as an array  vector  list  or sequence      JSON Structure          Here is an example of JSON data           firstName    John         lastName    Smith         address               streetAddress    21 2nd Street             city    New York             state    NY             postalCode   10021               phoneNumbers               212 555-1234             646 555-4567                JSON in JavaScript  JSON  in Javascript  is a string   People often assume all Javascript objects are JSON and that JSON is a Javascript object  This is incorrect   In Javascript var x    x y  is not JSON  this is a Javascript object  The two are not the same thing  The JSON equivalent  represented in the Javascript language  would be var x      x   y     x is an object of type string not an object in it s own right  To turn this into a fully fledged Javascript object you must first parse it  var x   JSON parse    x   y       x is now an object but this is not JSON anymore   See Javascript object Vs JSON    When working with JSON and JavaScript  you may be tempted to use the eval function to evaluate the result returned in the callback  but this is not suggested since there are two characters  U 2028  amp  U 2029  valid in JSON but not in JavaScript  read more of this here    Therefore  one must always try to use Crockford s script that checks for a valid JSON before evaluating it   Link to the script explanation is found here and here is a direct link to the js file  Every major browser nowadays has its own implementation for this   Example on how to use the JSON parser  with the json from the above code snippet      The callback function that will be executed once data is received from the server var callback   function  result        var johnny   JSON parse result         Now  the variable  johnny  is an object that contains all of the properties        from the above code snippet  the json example      alert johnny firstName         johnny lastName     Will alert  John Smith       The JSON parser also offers another very useful method  stringify   This method accepts a JavaScript object as a parameter  and outputs back a string with JSON format   This is useful for when you want to send data back to the server   var anObject    name   Andreas   surname    Grech   age   20   var jsonFormat   JSON stringify anObject     The above method will output this    name   Andreas   surname   Grech   age  20    The above two methods  parse and stringify  also take a second parameter  which is a function that will be called for every key and value at every level of the final result  and each value will be replaced by result of your inputted function    More on this here   Btw  for all of you out there who think JSON is just for JavaScript  check out this post that explains and confirms otherwise     References   JSON org Wikipedia Json in 3 minutes  Thanks mson   Using JSON with Yahoo  Web Services  Thanks gljivar  JSON to CSV Converter Alternative JSON to CSV Converter JSON Lint  JSON validator

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JSON  JavaScript Object Notation  is a lightweight format that is used for data interchanging   It is based on a subset of JavaScript language  the way objects are built in JavaScript   As stated in the MDN  some JavaScript is not JSON  and some JSON is not JavaScript   An example of  where this is used is web services responses   In the  old  days  web services used XML as their primary data format for transmitting back data  but since JSON appeared  The JSON format is specified in RFC 4627 by Douglas Crockford   it has been the preferred format because it is much more lightweight  You can find a lot more info on the official JSON web site   JSON is built on two structures    A collection of name value pairs  In various languages  this is realized as an object  record  struct  dictionary  hash table  keyed list  or associative array  An ordered list of values  In most languages  this is realized as an array  vector  list  or sequence      JSON Structure          Here is an example of JSON data           firstName    John         lastName    Smith         address               streetAddress    21 2nd Street             city    New York             state    NY             postalCode   10021               phoneNumbers               212 555-1234             646 555-4567                JSON in JavaScript  JSON  in Javascript  is a string   People often assume all Javascript objects are JSON and that JSON is a Javascript object  This is incorrect   In Javascript var x    x y  is not JSON  this is a Javascript object  The two are not the same thing  The JSON equivalent  represented in the Javascript language  would be var x      x   y     x is an object of type string not an object in it s own right  To turn this into a fully fledged Javascript object you must first parse it  var x   JSON parse    x   y       x is now an object but this is not JSON anymore   See Javascript object Vs JSON    When working with JSON and JavaScript  you may be tempted to use the eval function to evaluate the result returned in the callback  but this is not suggested since there are two characters  U 2028  amp  U 2029  valid in JSON but not in JavaScript  read more of this here    Therefore  one must always try to use Crockford s script that checks for a valid JSON before evaluating it   Link to the script explanation is found here and here is a direct link to the js file  Every major browser nowadays has its own implementation for this   Example on how to use the JSON parser  with the json from the above code snippet      The callback function that will be executed once data is received from the server var callback   function  result        var johnny   JSON parse result         Now  the variable  johnny  is an object that contains all of the properties        from the above code snippet  the json example      alert johnny firstName         johnny lastName     Will alert  John Smith       The JSON parser also offers another very useful method  stringify   This method accepts a JavaScript object as a parameter  and outputs back a string with JSON format   This is useful for when you want to send data back to the server   var anObject    name   Andreas   surname    Grech   age   20   var jsonFormat   JSON stringify anObject     The above method will output this    name   Andreas   surname   Grech   age  20    The above two methods  parse and stringify  also take a second parameter  which is a function that will be called for every key and value at every level of the final result  and each value will be replaced by result of your inputted function    More on this here   Btw  for all of you out there who think JSON is just for JavaScript  check out this post that explains and confirms otherwise     References   JSON org Wikipedia Json in 3 minutes  Thanks mson   Using JSON with Yahoo  Web Services  Thanks gljivar  JSON to CSV Converter Alternative JSON to CSV Converter JSON Lint  JSON validator

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What is JSON   JavaScript Object Notation  JSON  is a lightweight data-interchange format inspired by the object literals of JavaScript    JSON values can consist of   objects  collections of name-value pairs    arrays  ordered lists of values    strings  in double quotes    numbers   true  false  or null  JSON is language independent   JSON with PHP   After PHP Version 5 2 0  JSON extension is decodes and encodes functionalities as default   Json encode     - returns the JSON representation of values Json decode     - Decodes the JSON String Json last error - Returns the last error occured   JSON Syntax and Rules   JSON syntax is derived from JavaScript object notation syntax   Data is in name value pairs Data is separated by commas Curly braces hold objects Square brackets hold arrays

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In short  it is a scripting notation for passing data about  In some ways an alternative to XML  natively supporting basic data types  arrays and associative arrays  name-value pairs  called Objects because that is what they represent    The syntax is that used in JavaScript and JSON itself stands for  JavaScript Object Notation   However it has become portable and is used in other languages too   A useful link for detail is here   http   secretgeek net json 3mins asp

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Try the following code to parse your php json response  read php   lt script   src  https   code jquery com jquery-3 2 1 min js    integrity  sha256-hwg4gsxgFZhOsEEamdOYGBf13FyQuiTwlAQgxVSNgt4     crossorigin  anonymous  gt  lt  script gt   lt script type  text javascript  gt      ajax       url  index php       data         type  POST       success function result            jsondecoded     parseJSON result             each jsondecoded  function index  value                    servers   text     servers   text           value servername               console log value start               console log value end               console log value id                          statusCode        404  function           alert   page not found                    lt  script gt    server php   lt  php  echo     start   2017-08-29   end   2017-09-01   id   22     start   2017-09-03   end   2017-09-06   id   23        gt

User · Answer

the common short answer is  if you are using AJAX to make data requests  you can easily send and return objects as JSON strings  Available extensions for Javascript support toJSON   calls on all javascript types for sending data to the server in an AJAX request  AJAX responses can return objects as JSON strings which can be converted into Javascript objects by a simple eval call  e g  if the AJAX function someAjaxFunctionCallReturningJson returned        FirstName       Fred      LastName       Flintstone        you could write in Javascript  var obj   eval       someAjaxFunctionCallReturningJson   value         alert obj FirstName   alert obj LastName     JSON can also be used for web service payloads et al  but it is really convenient for AJAX results    Update  ten years later   Don t do this  use JSON parse

User · Answer

It s very simple  JSON stands for Java Script Object Notation  Think of it as an alternative to using XML for transferring data between software components    For example  I recently wrote a bunch of web services that returned JSON  and some Javascript developers then wrote code which called the services and consumed the information returned in that format

User · Answer

We have to do a project on college and we faced a very big problem  it is called Same Origin Policy  Amog other things  it makes that your XMLHttpRequest method from Javascript can t make requests to domains other than the domain that your site is on    For example you can t make request to www otherexample com if your site is on www example com  JSONRequest allows that  but you will get result in JSON format if that site allows that for example it has a web service that returns messages in JSON   That is one problem where you could use JSON perhaps   Here is something practical  Yahoo JSON

User · Answer

The Concept Explained - No Code or Technical Jargon What is JSON      How I explained it to my wifeTM Me     It   s basically a way of communicating with someone in writing    but with very specific rules  Wife  yeah      Me  In prosaic English  the rules are pretty loose  just like with cage fighting  Not so with JSON  There are many ways of describing something        Example 1  Our family has 4 people  You  me and 2 kids        Example 2  Our family  you  me  kid1 and kid2        Example 3  Family    you  me  kid1  kid2        Example 4  we got 4 people in our family  mum  dad  kid1 and kid2  Wife  Why don   t they just use plain English instead  Me  They would  but remember we   re dealing with computers  A computer is stupid and is not going to be able to understand sentences  So we gotta be really specific when computers are involved otherwise they get confused  Furthermore  JSON is a fairly efficient way of communicating  so most of the irrelevant stuff is cut out  which is pretty hand  If you wanted to communicate our family  to a computer  one way you could do so is like this         quot Family quot     quot Me quot    quot Wife quot    quot Kid1 quot    quot Kid2 quot             and that is basically JSON  But remember  you MUST obey the JSON grammar rules  If you break those rules  then a computer simply will not understand  i e  parse  what you are writing  Wife  So how do I write in Json  A good way would be to use a json serialiser - which is a library which does the heavy lifting for you  Summary  JSON is basically a way of communicating data to someone  with very  very specific rules  Using Key Value Pairs and Arrays  This is the concept explained  at this point it is worth reading the specific rules above

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In short - JSON is a way of serializing in such a way  that it becomes JavaScript code  When executed  with eval or otherwise   this code creates and returns a JavaScript object which contains the data you serialized  This is available because JavaScript allows the following syntax   var MyArray     1  2  3  4      MyArray is now an array with 4 elements var MyObject          StringProperty     Value        IntProperty    12       ArrayProperty      1  2  3        ObjectProperty       SubObjectProperty    SomeValue          MyObject is now an object with property values set    You can use this for several purposes  For one  it s a comfortable way to pass data from your server backend to your JavaScript code  Thus  this is often used in AJAX   You can also use it as a standalone serialization mechanism  which is simpler and takes up less space than XML  Many libraries exists that allow you to serialize and deserialize objects in JSON for various programming languages

User · Answer

The JSON format is often used for serializing and transmitting structured data over a network connection  It is used primarily to transmit data between a server and web application  serving as an alternative to XML

User · Answer

JSON Javascript object notation  is a light weight data format for data exchange transfer  Its in key value pair as the JavaScript is  For REST API its widely used for data transfer from server to client  Nowadays many of the social media sites are using this  Although I don t see this as robust as XML with respect of data types  XML has very rich datatypes and XSD  JSON is bit lacking in this   For same amount of string data JSON will be lighter compare to XML as XML has all that opening and closing tags  etc

User · Answer

In short  it is a scripting notation for passing data about  In some ways an alternative to XML  natively supporting basic data types  arrays and associative arrays  name-value pairs  called Objects because that is what they represent    The syntax is that used in JavaScript and JSON itself stands for  JavaScript Object Notation   However it has become portable and is used in other languages too   A useful link for detail is here   http   secretgeek net json 3mins asp

User · Answer

What is JSON   JavaScript Object Notation  JSON  is a lightweight data-interchange format inspired by the object literals of JavaScript    JSON values can consist of   objects  collections of name-value pairs    arrays  ordered lists of values    strings  in double quotes    numbers   true  false  or null  JSON is language independent   JSON with PHP   After PHP Version 5 2 0  JSON extension is decodes and encodes functionalities as default   Json encode     - returns the JSON representation of values Json decode     - Decodes the JSON String Json last error - Returns the last error occured   JSON Syntax and Rules   JSON syntax is derived from JavaScript object notation syntax   Data is in name value pairs Data is separated by commas Curly braces hold objects Square brackets hold arrays

User · Answer

It s very simple  JSON stands for Java Script Object Notation  Think of it as an alternative to using XML for transferring data between software components    For example  I recently wrote a bunch of web services that returned JSON  and some Javascript developers then wrote code which called the services and consumed the information returned in that format

User · Answer

JSON is JavaScript Object Notation  It is a much-more compact way of transmitting sets of data across network connections as compared to XML  I suggest JSON be used in any AJAX-like applications where XML would otherwise be the  recommended  option  The verbosity of XML will add to download time and increased bandwidth consumption        You can accomplish the same effect with JSON and its mark-up is almost exclusively dedicated to the data itself and not the underlying structure

User · Answer

We have to do a project on college and we faced a very big problem  it is called Same Origin Policy  Amog other things  it makes that your XMLHttpRequest method from Javascript can t make requests to domains other than the domain that your site is on    For example you can t make request to www otherexample com if your site is on www example com  JSONRequest allows that  but you will get result in JSON format if that site allows that for example it has a web service that returns messages in JSON   That is one problem where you could use JSON perhaps   Here is something practical  Yahoo JSON

User · Answer

The difference between JSON and conventional syntax would be as follows  in Javascript   Conventional   function Employee name  Id  Phone  email          this name   name        this Id   Id        this Phone   Phone        this email   email           access or call it as   var Emp   new Employee  mike   123   9373849784   mike Anderson office com      With JSON   if we use JSON we can define in different way as    function Employee args       this name   args name     this Id   args Id     this Phone   args Phone     this email   args email       now access this as     var Emp   new Employee   name   Mike    Id   123    Phone   23792747    email   mike adnersone office com       The important thing we have to remember is that   if we have to build the  Employee  class or modal with 100 elements without JSON method we have to parse everything when creating class  But with JSON we can define the objects inline only when a new object for the class is defined   so this line below is the way of doing things with JSON just a simple way to define things    var Emp   new Employee   name   Mike    Id   123    Phone   23792747    email   mike adnersone office com

User · Answer

JSON  JavaScript Object Notation  is a lightweight format that is used for data interchanging   It is based on a subset of JavaScript language  the way objects are built in JavaScript   As stated in the MDN  some JavaScript is not JSON  and some JSON is not JavaScript   An example of  where this is used is web services responses   In the  old  days  web services used XML as their primary data format for transmitting back data  but since JSON appeared  The JSON format is specified in RFC 4627 by Douglas Crockford   it has been the preferred format because it is much more lightweight  You can find a lot more info on the official JSON web site   JSON is built on two structures    A collection of name value pairs  In various languages  this is realized as an object  record  struct  dictionary  hash table  keyed list  or associative array  An ordered list of values  In most languages  this is realized as an array  vector  list  or sequence      JSON Structure          Here is an example of JSON data           firstName    John         lastName    Smith         address               streetAddress    21 2nd Street             city    New York             state    NY             postalCode   10021               phoneNumbers               212 555-1234             646 555-4567                JSON in JavaScript  JSON  in Javascript  is a string   People often assume all Javascript objects are JSON and that JSON is a Javascript object  This is incorrect   In Javascript var x    x y  is not JSON  this is a Javascript object  The two are not the same thing  The JSON equivalent  represented in the Javascript language  would be var x      x   y     x is an object of type string not an object in it s own right  To turn this into a fully fledged Javascript object you must first parse it  var x   JSON parse    x   y       x is now an object but this is not JSON anymore   See Javascript object Vs JSON    When working with JSON and JavaScript  you may be tempted to use the eval function to evaluate the result returned in the callback  but this is not suggested since there are two characters  U 2028  amp  U 2029  valid in JSON but not in JavaScript  read more of this here    Therefore  one must always try to use Crockford s script that checks for a valid JSON before evaluating it   Link to the script explanation is found here and here is a direct link to the js file  Every major browser nowadays has its own implementation for this   Example on how to use the JSON parser  with the json from the above code snippet      The callback function that will be executed once data is received from the server var callback   function  result        var johnny   JSON parse result         Now  the variable  johnny  is an object that contains all of the properties        from the above code snippet  the json example      alert johnny firstName         johnny lastName     Will alert  John Smith       The JSON parser also offers another very useful method  stringify   This method accepts a JavaScript object as a parameter  and outputs back a string with JSON format   This is useful for when you want to send data back to the server   var anObject    name   Andreas   surname    Grech   age   20   var jsonFormat   JSON stringify anObject     The above method will output this    name   Andreas   surname   Grech   age  20    The above two methods  parse and stringify  also take a second parameter  which is a function that will be called for every key and value at every level of the final result  and each value will be replaced by result of your inputted function    More on this here   Btw  for all of you out there who think JSON is just for JavaScript  check out this post that explains and confirms otherwise     References   JSON org Wikipedia Json in 3 minutes  Thanks mson   Using JSON with Yahoo  Web Services  Thanks gljivar  JSON to CSV Converter Alternative JSON to CSV Converter JSON Lint  JSON validator

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JSON  JavaScript Object Notation  is a lightweight format that is used for data interchanging   It is based on a subset of JavaScript language  the way objects are built in JavaScript   As stated in the MDN  some JavaScript is not JSON  and some JSON is not JavaScript   An example of  where this is used is web services responses   In the  old  days  web services used XML as their primary data format for transmitting back data  but since JSON appeared  The JSON format is specified in RFC 4627 by Douglas Crockford   it has been the preferred format because it is much more lightweight  You can find a lot more info on the official JSON web site   JSON is built on two structures    A collection of name value pairs  In various languages  this is realized as an object  record  struct  dictionary  hash table  keyed list  or associative array  An ordered list of values  In most languages  this is realized as an array  vector  list  or sequence      JSON Structure          Here is an example of JSON data           firstName    John         lastName    Smith         address               streetAddress    21 2nd Street             city    New York             state    NY             postalCode   10021               phoneNumbers               212 555-1234             646 555-4567                JSON in JavaScript  JSON  in Javascript  is a string   People often assume all Javascript objects are JSON and that JSON is a Javascript object  This is incorrect   In Javascript var x    x y  is not JSON  this is a Javascript object  The two are not the same thing  The JSON equivalent  represented in the Javascript language  would be var x      x   y     x is an object of type string not an object in it s own right  To turn this into a fully fledged Javascript object you must first parse it  var x   JSON parse    x   y       x is now an object but this is not JSON anymore   See Javascript object Vs JSON    When working with JSON and JavaScript  you may be tempted to use the eval function to evaluate the result returned in the callback  but this is not suggested since there are two characters  U 2028  amp  U 2029  valid in JSON but not in JavaScript  read more of this here    Therefore  one must always try to use Crockford s script that checks for a valid JSON before evaluating it   Link to the script explanation is found here and here is a direct link to the js file  Every major browser nowadays has its own implementation for this   Example on how to use the JSON parser  with the json from the above code snippet      The callback function that will be executed once data is received from the server var callback   function  result        var johnny   JSON parse result         Now  the variable  johnny  is an object that contains all of the properties        from the above code snippet  the json example      alert johnny firstName         johnny lastName     Will alert  John Smith       The JSON parser also offers another very useful method  stringify   This method accepts a JavaScript object as a parameter  and outputs back a string with JSON format   This is useful for when you want to send data back to the server   var anObject    name   Andreas   surname    Grech   age   20   var jsonFormat   JSON stringify anObject     The above method will output this    name   Andreas   surname   Grech   age  20    The above two methods  parse and stringify  also take a second parameter  which is a function that will be called for every key and value at every level of the final result  and each value will be replaced by result of your inputted function    More on this here   Btw  for all of you out there who think JSON is just for JavaScript  check out this post that explains and confirms otherwise     References   JSON org Wikipedia Json in 3 minutes  Thanks mson   Using JSON with Yahoo  Web Services  Thanks gljivar  JSON to CSV Converter Alternative JSON to CSV Converter JSON Lint  JSON validator

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In short  it is a scripting notation for passing data about  In some ways an alternative to XML  natively supporting basic data types  arrays and associative arrays  name-value pairs  called Objects because that is what they represent    The syntax is that used in JavaScript and JSON itself stands for  JavaScript Object Notation   However it has become portable and is used in other languages too   A useful link for detail is here   http   secretgeek net json 3mins asp

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Sometimes technicality is given where none is required  and while many of the top voted answers are accurately technical and specific  I personally don t think they are any more easy to understand  or succinct  as what can be found on Wikipedia  or in official documentation   The way I like to think of JSON is exactly what it is - a language within a world of different languages  However  the difference between JSON and other languages is that  everyone   speaks  JSON  along with their  native language    Using a real world example  let s pretend we have three people  One person speaks Igbo as their native tongue  The second person would like to interact with the first person  however  the first person speaks Yoruba as their first language   What can we do   Thankfully  the third person in our example grew up speaking English  but also happens to speak both Igbo and Yoruba as second languages  and so can act as an intermediary between the first two individuals   In the programming world  the first  person  is Python  the second  person  is Ruby  and the third  person  is JSON  who just so happens to be able to  translate  Ruby into Python and vice versa  Now obviously this analogy isn t a perfect one  but  as someone who is bilingual  I believe it s an easy way to look at how JSON interacts with other programming languages

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JSON is JavaScript Object Notation  It is a much-more compact way of transmitting sets of data across network connections as compared to XML  I suggest JSON be used in any AJAX-like applications where XML would otherwise be the  recommended  option  The verbosity of XML will add to download time and increased bandwidth consumption        You can accomplish the same effect with JSON and its mark-up is almost exclusively dedicated to the data itself and not the underlying structure

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In short  it is a scripting notation for passing data about  In some ways an alternative to XML  natively supporting basic data types  arrays and associative arrays  name-value pairs  called Objects because that is what they represent    The syntax is that used in JavaScript and JSON itself stands for  JavaScript Object Notation   However it has become portable and is used in other languages too   A useful link for detail is here   http   secretgeek net json 3mins asp

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We have to do a project on college and we faced a very big problem  it is called Same Origin Policy  Amog other things  it makes that your XMLHttpRequest method from Javascript can t make requests to domains other than the domain that your site is on    For example you can t make request to www otherexample com if your site is on www example com  JSONRequest allows that  but you will get result in JSON format if that site allows that for example it has a web service that returns messages in JSON   That is one problem where you could use JSON perhaps   Here is something practical  Yahoo JSON

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I like JSON mainly because it s so terse   For web content that can be gzipped  this isn t necessarily a big deal  hence why xhtml is so popular    But there are occasions where  this can be beneficial   For example  for one project I was transmitting information that needed to be serialized and transmitted via XMPP   Since most servers will limit the amount of data you can transmit in a single message  I found it helpful to use JSON over the obvious alternative  XML   As an added bonus  if you re familiar with Python or Javascript  you already pretty much know JSON and can interpret it without much training at all

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the common short answer is  if you are using AJAX to make data requests  you can easily send and return objects as JSON strings  Available extensions for Javascript support toJSON   calls on all javascript types for sending data to the server in an AJAX request  AJAX responses can return objects as JSON strings which can be converted into Javascript objects by a simple eval call  e g  if the AJAX function someAjaxFunctionCallReturningJson returned        FirstName       Fred      LastName       Flintstone        you could write in Javascript  var obj   eval       someAjaxFunctionCallReturningJson   value         alert obj FirstName   alert obj LastName     JSON can also be used for web service payloads et al  but it is really convenient for AJAX results    Update  ten years later   Don t do this  use JSON parse

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In the Java context  one reason why JSON might want to be used  is that it provides a very good alternative to Java s Serialization framework  which has been shown  historically  to be subject to some fairly serious vulnerabilities    Joshua Bloch discusses this in depth in Item 85  Prefer Alternatives to Java Serialization   Effective Java 3rd Edition   Java s Serialization was initially meant to translate data structures into a format that could be easily transmitted or stored  JSON meets this requirement  without the serious exploits referred to above

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the common short answer is  if you are using AJAX to make data requests  you can easily send and return objects as JSON strings  Available extensions for Javascript support toJSON   calls on all javascript types for sending data to the server in an AJAX request  AJAX responses can return objects as JSON strings which can be converted into Javascript objects by a simple eval call  e g  if the AJAX function someAjaxFunctionCallReturningJson returned        FirstName       Fred      LastName       Flintstone        you could write in Javascript  var obj   eval       someAjaxFunctionCallReturningJson   value         alert obj FirstName   alert obj LastName     JSON can also be used for web service payloads et al  but it is really convenient for AJAX results    Update  ten years later   Don t do this  use JSON parse

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In short - JSON is a way of serializing in such a way  that it becomes JavaScript code  When executed  with eval or otherwise   this code creates and returns a JavaScript object which contains the data you serialized  This is available because JavaScript allows the following syntax   var MyArray     1  2  3  4      MyArray is now an array with 4 elements var MyObject          StringProperty     Value        IntProperty    12       ArrayProperty      1  2  3        ObjectProperty       SubObjectProperty    SomeValue          MyObject is now an object with property values set    You can use this for several purposes  For one  it s a comfortable way to pass data from your server backend to your JavaScript code  Thus  this is often used in AJAX   You can also use it as a standalone serialization mechanism  which is simpler and takes up less space than XML  Many libraries exists that allow you to serialize and deserialize objects in JSON for various programming languages

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JSON is JavaScript Object Notation  It is a much-more compact way of transmitting sets of data across network connections as compared to XML  I suggest JSON be used in any AJAX-like applications where XML would otherwise be the  recommended  option  The verbosity of XML will add to download time and increased bandwidth consumption        You can accomplish the same effect with JSON and its mark-up is almost exclusively dedicated to the data itself and not the underlying structure

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In short - JSON is a way of serializing in such a way  that it becomes JavaScript code  When executed  with eval or otherwise   this code creates and returns a JavaScript object which contains the data you serialized  This is available because JavaScript allows the following syntax   var MyArray     1  2  3  4      MyArray is now an array with 4 elements var MyObject          StringProperty     Value        IntProperty    12       ArrayProperty      1  2  3        ObjectProperty       SubObjectProperty    SomeValue          MyObject is now an object with property values set    You can use this for several purposes  For one  it s a comfortable way to pass data from your server backend to your JavaScript code  Thus  this is often used in AJAX   You can also use it as a standalone serialization mechanism  which is simpler and takes up less space than XML  Many libraries exists that allow you to serialize and deserialize objects in JSON for various programming languages

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In short - JSON is a way of serializing in such a way  that it becomes JavaScript code  When executed  with eval or otherwise   this code creates and returns a JavaScript object which contains the data you serialized  This is available because JavaScript allows the following syntax   var MyArray     1  2  3  4      MyArray is now an array with 4 elements var MyObject          StringProperty     Value        IntProperty    12       ArrayProperty      1  2  3        ObjectProperty       SubObjectProperty    SomeValue          MyObject is now an object with property values set    You can use this for several purposes  For one  it s a comfortable way to pass data from your server backend to your JavaScript code  Thus  this is often used in AJAX   You can also use it as a standalone serialization mechanism  which is simpler and takes up less space than XML  Many libraries exists that allow you to serialize and deserialize objects in JSON for various programming languages

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Understanding JSON JSON is just a text format that most REST APIs use to return their data  Another common format is XML  but XML is quite a bit more verbose  Here   s a small example of JSON     JSON object      quot name quot    quot John quot      quot age quot   20       JSON array            quot name quot    quot John quot        quot age quot   20               quot name quot    quot Peter quot        quot age quot   22        Notice that the snippet starts with a brace    which indicates an object  JSON can also start as an array  which uses the square bracket   symbol to signify the start of the array  JSON needs to be properly formatted  so all beginning   and   symbols need to have their ending symbols    and    JSON can contain object or array  An object in JSON is wrapped inside the braces          while an array is wrapped inside square brackets          JSON structures data by key-value  Key is always a string  but value could be anything  String  number  JSON object  JSON array      This will affect the way we parse JSON in the next steps

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I like JSON mainly because it s so terse   For web content that can be gzipped  this isn t necessarily a big deal  hence why xhtml is so popular    But there are occasions where  this can be beneficial   For example  for one project I was transmitting information that needed to be serialized and transmitted via XMPP   Since most servers will limit the amount of data you can transmit in a single message  I found it helpful to use JSON over the obvious alternative  XML   As an added bonus  if you re familiar with Python or Javascript  you already pretty much know JSON and can interpret it without much training at all

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I like JSON mainly because it s so terse   For web content that can be gzipped  this isn t necessarily a big deal  hence why xhtml is so popular    But there are occasions where  this can be beneficial   For example  for one project I was transmitting information that needed to be serialized and transmitted via XMPP   Since most servers will limit the amount of data you can transmit in a single message  I found it helpful to use JSON over the obvious alternative  XML   As an added bonus  if you re familiar with Python or Javascript  you already pretty much know JSON and can interpret it without much training at all

[json] What is JSON and why would I use it?

Examples related to json