JavaScript namespace function

As a follow-up to my "Respecting the JavaScript global namespace" post, here's a function that can be used to quickly and easily create namespaces:

Update (2009-12-02): See my proposal to add the above namespace function to the base ECMAScript / JavaScript language.

Update (2016-11-27): Included as http://stackoverflow.com/questions/881515/how-do-i-declare-a-namespace-in-javascript/40835398#40835398.

(Updated to use a global function instead of extending the String prototype.)

var namespace = function(name, separator, container){
  var ns = name.split(separator || '.'),
    o = container || window,
    i,
    len;
  for(i = 0, len = ns.length; i < len; i++){
    o = o[ns[i]] = o[ns[i]] || {};
  }
  return o;
};

Here's the same code, compressed using YUI Compressor:

var namespace=function(c,f,b){var e=c.split(f||"."),g=b||window,d,a;for(d=0,a=e.length;d<a;d++){g=g[e[d]]=g[e[d]]||{}}return g};

Ideally, this function would be assigned to some other object (to respect the global namespace), unless accepted as a standard function as mentioned above.

See also:

• Namespacing made easy (kangax, 2008-01-30, thinkweb2.com)
• JavaScript Namespaces (Remy Sharp, 2008-02-04, remysharp.com)
• [1944624] Allow YAHOO.namespace To Create Arbitrary Namespaces (sourceforge.net/projects/yui/)

Unlike the "Namespacing made easy" post, this solution doesn't require Prototype. This solution also prevents overwriting existing objects and returns the created "namespace".

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();

Update (2008-05-13):

The concern was raised that the "len" variable in my for-loop is being created in the global scope / "namespace", which would contradict the entire purpose of this post! :-)

Fortunately, according to developer.mozilla.org, all variables declared after "var" are created within the same scope - and if declared within a function, the scope is that current function.

Here's my "test case". Use Firebug. First check that neither the "i" nor "len" variables already exist. Then run the following code, and note that neither variable is created in the global scope.

(function(){
  for(var i=0, len=0;false;){};
})();

Compared to this version, which does populate "len" into the global scope:

(function(){
  len = 0;
  for(var i=0;false;){};
})();

Maybe surprisingly, this makes "len" local again, even though it is assigned to before being declared with "var". This is because JavaScript does not have block scope.

(function(){
  len = 0;
  for(var i=0, len=0;false;){};
})();

This general practice is documented at http://www.prototypejs.org/api/array, where it is also explained how caching the length property is an aid to performance. (Though for the stated purpose of creating namespaces, which will probably only be handling single-digit lengths for the majority of the cases, the savings will be practically zero.)