模仿new

 1 Function.prototype.method = function (name, func) {
 2     this.prototype[name] = func;
 3 };
 4 Function.method("createInstance", function () {
 5     console.log("I was invoked!");
 6     var that = Object.create(this.prototype);
 7     var other = this.apply(that, arguments);
 8     return (typeof other === "object" && other) || that;
 9 });
10 var Person = function (name) {
11     this.name = name;
12 }.createInstance("Jack");//函数表达式后面可以直接调用函数的方法，但是函数声明不行。