Object.create()和Object.setPrototypeOf

简介

在原型写法中，我们常用Object.create()和Object.setPrototypeOf()，记录一下自己的学习理解

Object.create()

创建一个对象，直接上代码

function SuperClass(name) {
    this.name = name
    this.colors = ["red", "blue", "green"]
}
SuperClass.prototype.getName = function () {
    console.log(this.name)
}
const test3 = Object.create(new SuperClass("JJ"), {
    a: {
        value: 10,
    },
    b: {
        value: 20,
        writable: false,
    },
    name:{
        value:"TT"
    }
})
test3.getAB = function(){
    return this.a + this.b
}

通过下图可以看出，他的结果是创建了一个继承于SuperClass的新对象，但是细心可以发现，__proto__中少了一个constructor

使用其作为一个过渡函数实现继承

function SuperClass(name) {
    this.name = name
    this.colors = ["red", "blue", "green"]
}
SuperClass.prototype.getName = function () {
    return this.name
}
function SubClass(name, time) {
    SuperClass.call(this, name)
    this.time = time
}
// 为了不让SuperClass构造两遍，所以用空对象来过渡一下
SubClass.prototype = Object.create(SuperClass.prototype)
const test = new SubClass("TT", 2014)

此时，还是缺少了一个constructor，可以手动补充，SubClass.prototype.constructor = SubClass，然后在进行实例化

或使用Object.setPrototypeOf()来解决

Object.setPrototypeOf()

Object.setPrototypeOf就是字面意思，设置XXX的Prototype原型，所以上述可以将SubClass的原型设置为SuperClass的原型

function SuperClass2(name) {
    this.name = name
    this.colors = ["red", "blue", "green"]
}
SuperClass2.prototype.getName = function () {
    console.log(this.name)
}
function SubClass2(name, time) {
    SuperClass.call(this, name)
    this.time = time
}
Object.setPrototypeOf(SubClass2.prototype, SuperClass2.prototype)
SubClass2.prototype.getTime = function(){
    console.log(this.time)
}
const test2 = new SubClass2("TT", 2014)