function inside and outside subclass definition

arachide

Below are some code from cocos2dx-js binding official javascript sample

cc.Class = function(){};
cc.Class.extend = function (prop) { //John Resig's extend
    var _super = this.prototype;

    // Instantiate a base class (but only create the instance,
    // don't run the init constructor)
    initializing = true;
    var prototype = new this();
    initializing = false;
    fnTest = /xyz/.test(function(){xyz;}) ? /b_superb/ : /.*/;

    // Copy the properties over onto the new prototype
    for (var name in prop) {
        // Check if we're overwriting an existing function
        prototype[name] = typeof prop[name] == "function" &&
            typeof _super[name] == "function" && fnTest.test(prop[name]) ?
            (function (name, fn) {
                return function () {
                    var tmp = this._super;

                    // Add a new ._super() method that is the same method
                    // but on the super-class
                    this._super = _super[name];

                    // The method only need to be bound temporarily, so we
                    // remove it when we're done executing
                    var ret = fn.apply(this, arguments);
                    this._super = tmp;

                    return ret;
                };
            })(name, prop[name]) :
            prop[name];
    }

    // The dummy class constructor
    function Class() {
        // All construction is actually done in the init method
        if (!initializing && this.ctor)
            this.ctor.apply(this, arguments);
    }

    // Populate our constructed prototype object
    Class.prototype = prototype;

    // Enforce the constructor to be what we expect
    Class.prototype.constructor = Class;

    // And make this class extendable
    Class.extend = arguments.callee;

    return Class;
};


var Explosion = cc.Sprite.extend({
   tmpWidth:0,
   tmpHeight:0,
   active:true,
   ctor:function () {
   this._super();

   //blahblah
   },
   destroy:function () {
      //blahblah
   }
});

Explosion.sharedExplosion = function () {
   //blahblah
};

Just wonder why sharedExplosion is putted outside the definition of var Explosion