if (typeof Array.isArray === "undefined") {

   Array.isArray = function (arg) {

       return Object.prototype.toString.call(arg) === "[object Array]"

   };

}

Javascript继承-借用构造函数

var Widget = function (name) {

   this.messages = [];

};

Widget.prototype.type = 'Widget';

var SubWidget = function (name) {

   Widget.apply(this, Array.prototype.slice.call(arguments));

   this.name = name;

};

SubWidget.prototype = Widget.prototype;

var sub1 = new SubWidget('foo');

var sub2 = new SubWidget('bar');

sub1.messages.push('foo');

sub2.messages.push('bar');

console.log(sub1.messages);//foo

console.log(sub2.messages);//bar

Javascript原型-封装

var Dialog = (function () {

   function Dialog() {

   }

   Dialog.prototype = {

       init: function () {

           console.log("ok");

       }

   };

   return Dialog;

}());

var d = new Dialog();

d.init();//ok

通过闭包修正函数的上下文（浏览器不支持解决方案）