一、实例

        Person.prototype.name = 'sunny';

        function Person() {}

        var person = new Person();

        Person.prototype.name = 'cherry';

        console.log(person.name);  //cherry

        Person.prototype.name = 'sunny';

        function Person() {}

        Person.prototype.name = 'cherry';

        var person = new Person();

        console.log(person.name);   //cherry

        Person.prototype.name = 'sunny';

        function Person() {
            //var this = {__proto__ : Person.prototype}
        }

        var person = new Person();

        Person.prototype = {
            name : 'cherry'
        }

        console.log(person.name);  //sunny

这样理解

        var obj = {name : "a"};
        var obj1 = obj;
        obj = {name : "b"};

        Person.prototype = {name : "a"};
        __proto__ = Person.prototype;
        Person.prototype = {name : "b"};

new Person最后执行

        Person.prototype.name = 'sunny';

        function Person() {
            // var this = {__proto__ : Person.prototype}
        }

        Person.prototype = {
            name : 'cherry'
        }

        var person = new Person();

        console.log(person.name);   //cherry

二、隐式添加

        Person.prototype.name = 'abc';
        function Person() {
            // var this = {
            //  __proto__ : Person.prototype
            // }
        }

        var person = new Person();

三、继承

        // 继承  
        
        //1.圣杯模式
        function inherit(Target, Origin) {
            function F() {}
            F.prototype = Origin.prototype;
            Target.prototype = new F();
            Target.prototype.constructor = Target;
            Target.prototype.uber = Origin.prototype;
        }

        // 2.雅虎写法  闭包
        var inherit = (function () {
            var F = function () {}
            return function (Target, Origin) {
                F.prototype = Origin.prototype;
                Target.prototype = new F();
                Target.prototype.constructor = Target;
                Target.prototype.uber = Origin.prototype;
            }
        }());

        Father.prototype.lastName = "G";

        function Father() {}
        function Son() {}

        inherit(Son, Father);

        var son = new Son();
        var father = new Father();