How do I declare a namespace in JavaScript

Question

How do I create a namespace in JavaScript so that my objects and functions aren t overwritten by other same-named objects and functions  I ve used the following   if  Foo    null    typeof Foo      object     var Foo   new Object       Is there a more elegant or succinct way of doing this

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You can declare a simple function to provide namespaces   function namespace namespace        var object   this  tokens   namespace split       token       while  tokens length  gt  0            token   tokens shift             if  typeof object token       undefined                 object token                           object   object token              return object        Usage example namespace  foo bar   baz    I m a value

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I think you all use too much code for such a simple problem  No need to make a repo for that  Here s a single line function  namespace   gt  namespace split  quot   quot   reduce  last  next    gt   last next     last next           window    Try it    x000D   x000D     --- definition --- const namespace   name   gt  name split      reduce  last  next    gt   last next     last next           window       --- Use ---- const c   namespace  a b c    c MyClass   class MyClass         --- see ---- console log  a      a   x000D   x000D   x000D

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I created namespace which is inspired by Erlang s modules  It is a very functional approach  but that is how I write my JavaScript code these days   It gives a closure a global namespace and exposes a defined set functions within that closure    function       namespace  images   previous  next           This creates or finds a root object  images  and binds the two functions to it       It works even though those functions are not yet defined     function previous             function next             function find             A private function

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Here s how Stoyan Stefanov does it in his JavaScript Patterns book which I found to be very good  it also shows how he does comments that allows for auto-generated API documentation  and how to add a method to a custom object s prototype          My JavaScript application      module myapp          namespace Namespace for MYAPP classes and functions     var MYAPP   MYAPP               A maths utility    namespace MYAPP    class math stuff    MYAPP math stuff                    Sums two numbers              method sum        param  Number  a First number        param  Number  b Second number        return  Number  Sum of the inputs            sum  function  a  b            return a   b                        Multiplies two numbers              method multi        param  Number  a First number        param  Number  b Second number        return  Number  The inputs multiplied            multi  function  a  b            return a   b                  Constructs Person objects    class Person    constructor    namespace MYAPP    param  String  First name    param  String  Last name    MYAPP Person   function  first  last                   First name of the Person        property first name        type String            this first name   first                 Last name of the Person        property last name        type String            this last name   last            Return Person s full name      method getName    return  String  First name   last name    MYAPP Person prototype getName   function          return this first name         this last name

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Is there a more elegant or succinct way of doing this    Yes  For example   var your namespace   your namespace          then you can have   var your namespace   your namespace        your namespace Foo    toAlert  test    your namespace Bar   function arg         alert arg      with your namespace       Bar Foo toAlert

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If using a Makefile you can do this      prelude hjs billy   new       function moduleWrapper          const exports   this      postlude hjs return exports            someinternalfile js function bob      console log  hi      exports bob   bob      clientfile js billy bob      I prefer to use a Makefile anyway once I get to about 1000 lines because I can effectively comment out large swaths of code by removing a single line in the makefile  It makes it easy to fiddle with stuff  Also  with this technique the namespace only appears once in the prelude so it s easy to change and you don t have to keep repeating it inside the library code   A shell script for live development in the browser when using a makefile   while  true   do make  sleep 1  done   Add this as a make task  go  and you can  make go  to keep your build updated as you code

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I m 7 years late to the party  but did quite a bit of work around this 8 years ago    http   blogger ziesemer com 2008 05 javascript-namespace-function html http   blogger ziesemer com 2007 10 respecting-javascript-global-namespace html   It is important to be able to easily and efficiently create multiple nested namespaces to keep a complex web application organized and manageable  while respecting the JavaScript global namespace  preventing namespace pollution   and with not clobbering any existing objects in the namespace path while doing so   From the above  this was my circa-2008 solution   var namespace   function name  separator  container     var ns   name split separator              o   container    window      i      len    for i   0  len   ns length  i  lt  len  i         o   o ns i     o ns i                return o       This isn t creating a namespace  but provides a function for creating namespaces   This can be condensed to a minified one-liner   var namespace function c f b  var e c split f       g b  window d a for d 0 a e length d lt a d    g g e d   g e d       return g     Example of use   namespace  com example namespace    com example namespace test   function      alert  In namespaced function          Or  as one statement   namespace  com example namespace   test   function      alert  In namespaced function          Either is then executed as   com example namespace test      If you don t need support for legacy browsers  an updated version   const namespace   function name  separator  container       var o   container    window      name split separator         forEach function x           o   o x    o x                     return o       Now  I d be leery of exposing namespace to the global namespace itself    Too bad the base language doesn t provide this for us    So I d typically use this myself in a closure  such as    x000D   x000D   function    x000D   const namespace   function name  separator  container   x000D    var o   container    window  x000D    name split separator         forEach function x   x000D     o   o x    o x         x000D        x000D    return o  x000D      x000D   const ns   namespace  com ziesemer myApp    x000D    x000D      Optional  x000D   ns namespace   ns  x000D    x000D      Further extend  work with ns from here    x000D        x000D   x000D  console log    com      com   x000D   x000D   x000D    In a larger application  this only needs to be defined once at the beginning of a page load  for client-based web apps    Additional files can then reuse the namespace function if kept  included as  optional  in the above    At worst  if this function is re-declared a few times - it s only a few lines of code  and less if minified

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JavaScript doesn   t support namespace by default  So if you create any element function  method  object  variable  then it becomes global and pollute the global namespace  Let s take an example of defining two functions without any namespace   function func1         console log  This is a first definition       function func1         console log  This is a second definition      func1       This is a second definition   It always calls the second function definition  In this case  namespace will solve the name collision problem

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This is a follow-up to user106826 s link to Namespace js  It seems the project moved to GitHub  It is now smith namespacedotjs   I have been using this simple JavaScript helper for my tiny project and so far it seems to be light yet versatile enough to handle namespacing and loading modules classes  It would be great if it would allow me to import a package into a namespace of my choice  not just the global namespace    sigh  but that s besides the point   It allows you to declare the namespace then define objects modules in that namespace   Namespace  my awesome package    my awesome package WildClass         Another option is to declare the namespace and its contents at once   Namespace  my awesome package         SuperDuperClass            saveTheDay  function                 alert  You are welcome                           For more usage examples  look at the example js file in the source

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I like Jaco Pretorius  solution  but I wanted to make the  this  keyword a bit more useful by pointing it to the module namespace object  My version of skillet    function     undefined         console log this       call window myNamespace   window myNamespace        jQuery

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My favorite pattern has become lately this    x000D   x000D  var namespace    function     x000D     x000D       expose to public x000D    return   x000D      a  internalA  x000D      c  internalC x000D      x000D   x000D       all private x000D     x000D        x000D       Full JSDoc x000D        x000D    function internalA     x000D             x000D      x000D     x000D        x000D       Full JSDoc x000D        x000D    function internalB     x000D             x000D      x000D     x000D        x000D       Full JSDoc x000D        x000D    function internalC     x000D             x000D      x000D     x000D        x000D       Full JSDoc x000D        x000D    function internalD     x000D             x000D      x000D     x000D        x000D   x000D   x000D    Of course  return can be at the end  but if only function declarations follow it  it s much easier to see what s the namespace all about  and what API is exposed   The pattern of using function expressions in such cases results in not being able to know what methods are exposed without going over the entire code

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If you need the private scope   var yourNamespace    function          Private property   var publicScope            Private property   var privateProperty    aaa         Public property   publicScope publicProperty    bbb        Public method   publicScope publicMethod   function         this privateMethod              Private method   function privateMethod         console log this privateProperty            Return only the public parts   return publicScope         yourNamespace publicMethod      else if you won t ever use the private scope   var yourNamespace        yourNamespace publicMethod   function            Do something        yourNamespace publicMethod2   function            Do something        yourNamespace publicMethod

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I like this   var yourNamespace          foo  function                 bar  function                    yourNamespace foo

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Another way to do it  which I consider it to be a little bit less restrictive than the object literal form  is this   var ns   new function          var internalFunction   function                  this publicFunction   function                  The above is pretty much like the module pattern and whether you like it or not  it allows you to expose all your functions as public  while avoiding the rigid structure of an object literal

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I ve written another namespacing library that works a bit more like packages   units do in other languages  It allows you to create a package of JavaScript code and the reference that package from other code   File hello js  Package  hello       function       function greeting         alert  Hello World              Expose function greeting to other packages   Export  greeting   greeting         File Example js  Package  example     hello    function greeting         Greeting is available here   greeting        Alerts   Hello World         Only the second file needs to be included in the page  Its dependencies  file hello js in this example  will automatically be loaded and the objects exported from those dependencies will be used to populate the arguments of the callback function   You can find the related project in Packages JS

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I use this approach   var myNamespace      myNamespace  construct   function         var staticVariable    This is available to all functions created here       function MyClass                   Depending on the class  we may build all the classes here        this publicMethod   function                        Do stuff                        Alternatively  we may use a prototype      MyClass prototype altPublicMethod   function                   Do stuff            function privateStuff                    function publicStuff                   Code that may call other public and private functions               List of things to place publically     this publicStuff   publicStuff     this MyClass   MyClass   myNamespace  construct       The following may or may not be in another file myNamespace subName      myNamespace subName  construct   function           Build namespace   myNamespace subName  construct     External code can then be   var myClass   new myNamespace MyClass    var myOtherClass   new myNamepace subName SomeOtherClass    myNamespace subName publicOtherStuff someParameter

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My habit is to use function myName   as property storage  and then var myName as  method  holder     Whether this is legitimate enough or not  beat me  I am relying on my PHP logic all the time  and things simply work   D  function myObj         this prop1   1      this prop2   2      this prop3    string      var myObj       myObj instanceof Function     false     Object create          props  new myObj         fName1  function        code               fName2  function        code                console log  Object creation failed         if  this     that  myObj fName1    else myObj fName2        You can also do it in a  vice versa  way to check before object creation which is much better    function myObj         this prop1   1      this prop2   2      this prop3    string      var myObj          typeof myObj       function     myObj instanceof Function     false        new Boolean         Object create            props  new myObj            init  function      return             fName1  function        code                  fName2  function        code                    if  myObj instanceof Boolean        Object freeze myObj       console log  myObj failed         debugger    else     myObj init      Reference to this  JavaScript  Creating Object with Object create

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We can use it independently in this way   var A   A       A B        A B         itemOne  null      itemTwo  null      A B itemOne   function                  A B itemTwo   function

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The Module pattern was originally defined as a way to provide both private and public encapsulation for classes in conventional software engineering   When working with the Module pattern  we may find it useful to define a simple template that we use for getting started with it  Here s one that covers name-spacing  public and private variables   In JavaScript  the Module pattern is used to further emulate the concept of classes in such a way that we re able to include both public private methods and variables inside a single object  thus shielding particular parts from the global scope  What this results in is a reduction in the likelihood of our function names conflicting with other functions defined in additional scripts on the page   var myNamespace    function         var myPrivateVar  myPrivateMethod        A private counter variable   myPrivateVar   0        A private function which logs any arguments   myPrivateMethod   function  foo           console log  foo            return           A public variable     myPublicVar   foo           A public function utilizing privates     myPublicFunction  function  bar               Increment our private counter       myPrivateVar              Call our private method using bar       myPrivateMethod  bar                         Advantages  why is the Module pattern a good choice  For starters  it s a lot cleaner for developers coming from an object-oriented background than the idea of true encapsulation  at least from a JavaScript perspective   Secondly  it supports private data - so  in the Module pattern  public parts of our code are able to touch the private parts  however the outside world is unable to touch the class s private parts   Disadvantages  The disadvantages of the Module pattern are that as we access both public and private members differently  when we wish to change visibility  we actually have to make changes to each place the member was used   We also can t access private members in methods that are added to the object at a later point  That said  in many cases the Module pattern is still quite useful and when used correctly  certainly has the potential to improve the structure of our application   The Revealing Module Pattern  Now that we re a little more familiar with the module pattern  let   s take a look at a slightly improved version - Christian Heilmann   s Revealing Module pattern   The Revealing Module pattern came about as Heilmann was frustrated with the fact that he had to repeat the name of the main object when we wanted to call one public method from another or access public variables He also disliked the Module pattern   s requirement for having to switch to object literal notation for the things he wished to make public   The result of his efforts was an updated pattern where we would simply define all of our functions and variables in the private scope and return an anonymous object with pointers to the private functionality we wished to reveal as public   An example of how to use the Revealing Module pattern can be found below  var myRevealingModule    function               var privateVar    Ben Cherry               publicVar    Hey there             function privateFunction                 console log   Name     privateVar                       function publicSetName  strName                 privateVar   strName                     function publicGetName                 privateFunction                           Reveal public pointers to            private functions and properties          return               setName  publicSetName              greeting  publicVar              getName  publicGetName                        myRevealingModule setName   Paul Kinlan       Advantages  This pattern allows the syntax of our scripts to be more consistent  It also makes it more clear at the end of the module which of our functions and variables may be accessed publicly which eases readability   Disadvantages  A disadvantage of this pattern is that if a private function refers to a public function  that public function can t be overridden if a patch is necessary  This is because the private function will continue to refer to the private implementation and the pattern doesn t apply to public members  only to functions   Public object members which refer to private variables are also subject to the no-patch rule notes above

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In JavaScript there are no predefined methods to use namespaces  In JavaScript we have to create our own methods to define NameSpaces  Here is a procedure we follow in Oodles technologies   Register a NameSpace Following is the function to register a name space    Register NameSpaces Function function registerNS args    var nameSpaceParts   args split        var root   window    for var i 0  i  lt  nameSpaceParts length  i         if typeof root nameSpaceParts i       undefined      root nameSpaceParts i     new Object       root   root nameSpaceParts i           To register a Namespace just call the above function with the argument as name space separated by      dot   For Example Let your application name is oodles  You can make a namespace by following method  registerNS  oodles HomeUtilities    registerNS  oodles GlobalUtilities    var  OHU   oodles HomeUtilities  var  OGU   oodles GlobalUtilities    Basically it will create your NameSpaces structure like below in backend   var oodles          HomeUtilities            GlobalUtilities           In the above function you have register a namespace called  oodles HomeUtilities  and  oodles GlobalUtilities   To call these namespaces we make an variable i e  var  OHU and var  OGU   These variables are nothing but an alias to Intializing the namespace  Now  Whenever you declare a function that belong to HomeUtilities you will declare it like following    OHU initialization   function          Your Code Here      Above is the function name initialization and it is put into an namespace  OHU  and to call this function anywhere in the script files  Just use following code    OHU initialization      Similarly  with the another NameSpaces   Hope it helps

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Quite a follow-up of Ionu  G  Stan s answer  but showing the benefits of uncluttered code by using var ClassFirst   this ClassFirst   function          which takes advantage of JavaScript s closure scoping for less namespace cluttering for classes in the same namespace   var Namespace   new function         var ClassFirst   this ClassFirst   function             this abc   123             var ClassSecond   this ClassSecond   function             console log  Cluttered way to access another class in namespace     new Namespace ClassFirst   abc           console log  Nicer way to access a class in same namespace     new ClassFirst   abc            var Namespace2   new function         var ClassFirst   this ClassFirst   function             this abc   666             var ClassSecond   this ClassSecond   function             console log  Cluttered way to access another class in namespace     new Namespace2 ClassFirst   abc           console log  Nicer way to access a class in same namespace     new ClassFirst   abc            new Namespace ClassSecond   new Namespace2 ClassSecond     Output   Cluttered way to access another class in namespace  123 Nicer way to access a class in same namespace  123 Cluttered way to access another class in namespace  666 Nicer way to access a class in same namespace  666

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After porting several of my libraries to different projects  and having to constantly be changing the top level  statically named  namespace  I ve switched to using this small  open source  helper function for defining namespaces   global namespace Define  startpad base   function ns        var Other   ns Import  startpad other                   Description of the benefits are at my blog post   You can grab the source code here   One of the benefits I really like is isolation between modules with respect to load order   You can refer to an external module BEFORE it is loaded   And the object reference you get will be filled in when the code is available

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Sample   var namespace       namespace module1    function         var self           self initialized   false       self init   function            setTimeout self onTimeout  1000              self onTimeout   function            alert  onTimeout           self initialized   true              self init       If it needs to auto-initialize            You can also call  namespace module1 init     from outside the module         return self         You can optionally declare a local variable  same  like self and assign local onTimeout if you want it to be private

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I normally build it in a closure   var MYNS   MYNS         MYNS subns    function          function privateMethod                Do private stuff  or build internal          return  Message              return           someProperty   prop value           publicMethod  function                 return privateMethod       stuff                            My style over the years has had a subtle change since writing this  and I now find myself writing the closure like this   var MYNS   MYNS         MYNS subns    function         var internalState    Message        var privateMethod   function                Do private stuff  or build internal          return internalState             var publicMethod   function             return privateMethod       stuff               return           someProperty   prop value           publicMethod  publicMethod                In this way I find the public API and implementation easier to understand  Think of the return statement as being a public interface to the implementation

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Because you may write different files of JavaScript and later combine or not combine them in an application  each needs to be able to recover or construct the namespace object without damaging the work of other files     One file might intend to use the namespace namespace namespace1   namespace   window namespace        namespace namespace1   namespace namespace1         namespace namespace1 doSomeThing   function       Another file might want to use the namespace namespace namespace2   namespace   window namespace        namespace namespace2   namespace namespace2         namespace namespace2 doSomeThing   function       These two files can live together or apart without colliding

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I use the approach found on the Enterprise jQuery site  Here is their example showing how to declare private  amp  public properties and functions  Everything is done as a self-executing anonymous function   function  skillet     undefined           Private Property     var isHot   true         Public Property     skillet ingredient    quot Bacon Strips quot          Public Method     skillet fry   function             var oliveOil           addItem   quot  t n Butter  n t quot             addItem  oliveOil            console log   quot Frying  quot    skillet ingredient                  Private Method     function addItem  item             if   item     undefined                 console log   quot Adding  quot      trim item                        window skillet   window skillet        jQuery      So if you want to access one of the public members you would just go skillet fry   or skillet ingredients  What s really cool is that you can now extend the namespace using the exact same syntax    Adding new Functionality to the skillet  function  skillet     undefined           Private Property     var amountOfGrease    quot 1 Cup quot          Public Method     skillet toString   function             console log  skillet quantity    quot   quot                         skillet ingredient    quot   amp   quot                         amountOfGrease    quot  of Grease quot             console log  isHot    quot Hot quot     quot Cold quot               window skillet   window skillet        jQuery      The third undefined argument  The third  undefined argument is the source of the variable of value undefined  I m not sure if it s still relevant today  but while working with older browsers   JavaScript standards  ecmascript 5  javascript  lt  1 8 5   firefox 4   the global-scope variable undefined is writable  so anyone could rewrite its value  The third argument  when not passed a value  creates a variable named undefined which is scoped to the namespace function  Because no value was passed when you created the name space  it defaults to the value undefined

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I use the following syntax for the namespace   var MYNamespace   MYNamespace         MYNamespace MyFirstClass   function  val            this value   val          this getValue   function                              return this value                                   var myFirstInstance   new MYNamespace MyFirstClass 46   alert myFirstInstance getValue       jsfiddle  http   jsfiddle net rpaul 4dngxwb3 1

[javascript] How do I declare a namespace in JavaScript?

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