namespace.js

;
(function (root, undefined) {
  'use strict';

  var toString = Object.prototype.toString;
  
  if (toString.call(root.namespace) === '[object Function]') {
    return;
  }

  root.namespace = function (ns, parent) {
    var parts,
        index,
        length;

    if (toString.call(ns) !== '[object String]') {
      throw new Error('Invalid namespace: ' + ns);
    }

    parts = ns.split('.');
    parent = parent || root;

    for (index = 0, length = parts.length; index < length; index += 1) {
      if (typeof parent[parts[index]] === 'undefined') {
        parent[parts[index]] = {};
      }

      parent = parent[parts[index]];
    }

    return parent;
  };
})(this);

// var modules = namespace('app.modules'); -> app.modules = {}
// var moduleA = namespace('app.modules.moduleA'); -> app.modules.moduleA = {}
// var moduleB = namespace('moduleB', modules); -> app.modules.moduleB = {}