(function(){
    var initializing = false, fnTest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /.*/;

    // The base Class implementation (does nothing)
    this.TestExend = function(){};

    var self = this;
    // Create a new Class that inherits from this class
    this.TestExend.extend = function(prop) {
        var _super = this.prototype;

        console.log("Test : " + self == this);
        // Instantiate a base class (but only create the instance,
        // don't run the init constructor)
        initializing = true;
        var prototype = new this();（this指向的是TestExend本身）
        initializing = false;

        // 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 DummyTest() {
            // All construction is actually done in the init method
            if ( !initializing && this.init )
                this.init.apply(this, arguments);
        }

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

        // Enforce the constructor to be what we expect
        DummyTest.prototype.constructor = DummyTest;
        // And make this class extendable
        DummyTest.extend = arguments.callee;

        return DummyTest;
    };
    
})();

var Animal= TestExend.extend({
    init: function(isAnimal){
        this.testPerson= isAnimal
;
    }
});

var Person = Animal.extend({
    init: function(){
        this._super( false );
    }
});

var tmpAnimal = new Animal(true);

var tmpPerson = new Person();

实现提示：

当一个函数作为一个对象的方法去调用,this指向的是对象本身.
    下面的例子中,当 o.f()被调用,函数里面的this指向的是 o对象.

var o = {
    prop: 37,
    f: function() {
        return this.prop;
    }
};

console.log(o.f()); // logs 37
假如 o 对象只申明了一个属性,其f方法在开始声明时还没有被定义,
    然后通过o.f直接被赋值为其他方法,其最后的效果也是一样的,

var o = {prop: 37};

function independent() {
    return this.prop;
}

o.f = independent;

console.log(o.f()); // logs 37