第一种:通过prototype来实现

prototype.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <script type="text/javascript">
        function Person(){}

        Person.prototype.username = "lisi";
        Person.prototype.gender = "man";
        Person.prototype.fav = ["read","eat"];


        var p1 = new Person();
        var p2 = new Person();
        p2.username = "zhangsan";
        //p2.fav.push("run");
        var fav = p2.fav;
        console.log(fav)
        p2.fav = new Array();
        p2.fav = p2.fav.concat(fav);

        p2.fav.push("run");

        /*console.log(p1.username);
         console.log(p1.fav);
         console.log(p2.username);
         console.log(p2.fav);*/

        function User(){}
        User.prototype = new Person();
        User.prototype.password = "123123";
        User.prototype.email = "admin@admin.com";

        User.prototype.say = function(){
            console.log(this);
        };

        var u = new User();
        u.gretting="Hello";
        var u1 = new User();

        console.log(u.username)
        u.say();
        u1.say();

    </script>
</head>
<body>

</body>
</html>

第二种方法:通过this关键字来实现;js中的this始终指向调用它的对象
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <script type="text/javascript">
        function Person(name,gender){
            this.name = name;
            this.gender = gender;
        }
        
        function User(name,gender,email,password){
            this.super = Person;
            this.super(name,gender);
            delete this.super;
            this.email = email;
            this.password = password;
            //this.Person(name,gender);
        }

        var p1 = new Person("lisi","man");

        var u = new User("zhangsan","msn","zhnagsan@zhangsan.com","123123123");
        console.log(p1.name);
        console.log(u.name);
        //var p2 = new Person();
        //p2.name = "lisi";
        //p2.gender = "man";
    </script>
</head>
<body>

</body>
</html>

第三种方法:通过call或者apply来实现
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <script type="text/javascript">
        function Person(name,gender){
            this.name = name;
            this.gender = gender;
        }

        function User(name,gender,email){

            //对象冒充  动态改变 函数的执行上下文
            //Person.call(this,name,gender);
            Person.apply(this,[name,gender]);

            this.email = email;

            this.say = function(msg){
                console.log(this);
                console.log(msg);
            }
        }

        var u = new User("lisi","man","lisi@lisi.com");
        console.log(u.gender);
        u.say("Hello");

        u.say.call(new Person("",""),"Hello1");
        u.say.apply(window,["lisi"]);

        console.log("--------------------")
        var name = "lisi";
        var obj = {
            name:"zhangsan",
            say:function(){
                console.log(this.name);
                return function(){
                    console.log(this.name);
                    return function(){
                        console.log(this.name);
                        return {
                            name:"wangwu",
                            say:function(){
                                console.log(this.name);
                            }

                        }
                    }
                }
            }
        };

        obj.say().call(obj)().say.apply(this);


        //obj.say()();
    </script>
</head>
<body>

</body>
</html>