A 对象通过继承 B 对象，就能直接拥有 B 对象的所有属性和方法。

1. 基于原型继承

//父类
function Shape(){
    this.x = 0
    this.y = 0
}
//父类的方法
Shape.prototype.move = function(x, y){
    this.x += x
    this.y += y
    console.log('Shape moved')
}
//子类
function Rectangle(){
    Shape.call(this)
}
//子类继承父类
Rectangle.prototype = Object.create(Shape.prototype)
Rectangle.prototype.constructor = Rectangle

const rect = new Rectangle()

console.log(rect instanceof Rectangle)    //true
console.log(rect instanceof Shape)     //true
rect.hasOwnProperty('move')    //false
rect.move(1, 1)    //Shape moved

如果希望能继承到多个对象（多重继承），可以使用混入的方式

function B1(){
    this.x = 1
}
B1.prototype.hello = 'hello'
function B2(){
    this.y = 2
} 
B2.prototype.world = 'world'

function A(){
    B1.call(this)
    B2.call(this)
}

//继承B1
A.prototype = Object.create(B1.prototype)
//加入B2
Object.assign(A.prototype, B2.prototype)

A.prototype.constructor = A

const a = new A()
a.x  //1
a.y  //2
a.hello  //hello
a.world  //world

2. 基于 class 的继承

//父类
class Person{
    constructor(name, age){
        this.name = name
        this.age = age
    }
    showName(){
        console.log(this.name, this.age)
    }
}

//子类
class Student extends Person{
    constructor(name, age, major){
        //通过super调用父类的方法
        super(name, age)  
        this.major = major
    }
    showName(){
        console.log(this.name, this.age, this.major)
    }
}

const p1 = new Person('小红', 18)
const s1 = new Student('小明', 19, 'Chemistry')
p1.showName  //小红 18
p2.showName  //小明 19 Chemistry