<script>

        var name = "global";

        function fn(){

            console.log(this.name);

        };

        fn();//函数申明式，this指向全局，"global"

        var obj ={

            name:"object",

            say:function(){

                console.log(this.name);

            }

        }

        obj.say();//对象中调用，this指向当前对象，"object"

        function Person(){

            this.name="person";

            this.say=function(){

                console.log(this.name);

            }

        }

        var p = new Person();

        p.say();//构造函数中调用指向当前构造函数，“person”

    </script>

    <script>

        function Parent(){

            this.name = "zzz";

            this.age = 233;

        };

        function Child(){

            Parent.call(this);

            this.favor = "dance";

        }

        var p = new Parent();

        var c = new Child();

        console.log(p);//{name: "zzz", age: 233}

        console.log(c);//{name: "zzz", age: 233, favor: "dance"}

    </script>

    <script>

        function Parent(){

            this.name = "zzz";

            this.age = 23;

        };

        function Child(){

            this.favor = "dance";

        }

        Parent.prototype.id=233;

        Child.prototype = new Parent();

        var c = new Child();

        console.log(c.id);//

    </script>