JS通过prototype实现继承的简单示例:

var MYJS={};
MYJS.extend=function(baseClass, prop) {

	if (typeof (baseClass) === "object") {
		prop = baseClass;
		baseClass = null;
	}
	// 本次调用所创建的类（构造函数）
	function F() {
	}
	// 如果此类需要从其它类扩展
	if (baseClass) {
		F.prototype = new baseClass();
		F.prototype.constructor = F;
	}

	// 覆盖父类的同名函数
	for (var name in prop) {
		if (prop.hasOwnProperty(name)) {
			F.prototype[name] = prop[name];
		}
	}
	return F;
};

<script>
        function Cls1(){
            this.name="Cls1 class";
            this.fun1 =function(){
                console.log("Cls1.fun1");
            };
        }
        var Cls2 = MYJS.extend(Cls1, 
            {
                a:'a',
                fun2:function(){
                    console.log("Cls2.fun2");
                }
        });

        var Cls3 = MYJS.extend(Cls2, 
            {
                a:'cls3.b',
                b:'b',
                fun3:function(){
                    console.log("Cls3.fun3");
                }
        });
        var obj3 = new Cls3();
        console.log(obj3.name);
        console.log(obj3.a);
        console.log(obj3.b);
        obj3.fun1();
        obj3.fun2();
        obj3.fun3();
       
    </script>