ES5 和 ES6 继承比较：

ES5构造函数和继承：

// ES5构造函数
function User(name, pass) {
    this.name = name;
    this.pass = pass;
}

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

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

var u1 = new User('Guofq', 123123);
u1.showName();
u1.showPass();

// ES5继承
function Vipuser(name, pass, level) {
    console.log(this);
    User.apply(this, [name, pass]);
    this.level = level;
}

Vipuser.prototype = new User();
Vipuser.prototype.constructor = Vipuser;
Vipuser.prototype.showLevel = function() {
    console.log(this.level);
}

var v1 = new Vipuser('Zhangs', 123123, 12);
v1.showName();
v1.showPass();
v1.showLevel();

ES6构造函数和继承：

// ES6构造函数
class User2 {
    constructor(name, pass) {
        this.name = name;
        this.pass = pass;
    }
    showName() {
        console.log(this.name);
    }
    showPass() {
        console.log(this.pass);
    }
}

let u2 = new User2('Lis', 123456);
u2.showName();
u2.showPass();

// ES6继承
class Vipuser2 extends User2 {
    constructor(name, pass, level) {
        super(name, pass);
        this.level = level;
    }
    showLevel() {
        console.log(this.level);
    }
}

let v2 = new Vipuser2('Wangw', 12345678, 6);
v2.showName();
v2.showPass();
v2.showLevel();