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Javascript的ES5,ES6的7種繼承詳解

更新時(shí)間：2022年02月28日 11:20:35 作者：arzh

這篇文章主要為大家詳細(xì)介紹了Javascript的ES5,ES6的7種繼承，文中示例代碼介紹的非常詳細(xì)，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下，希望能夠給你帶來幫助

眾所周知，在ES6之前，前端是不存在類的語法糖，所以不能像其他語言一樣用extends關(guān)鍵字就搞定繼承關(guān)系，需要一些額外的方法來實(shí)現(xiàn)繼承。下面就介紹一些常用的方法，紅寶書已經(jīng)概括的十分全面了，所以本文基本就是對(duì)紅寶書繼承篇章的筆記和梳理。

原型鏈繼承

function Parent() {
    this.name = 'arzh'
}
Parent.prototype.getName = function () {
    console.log(this.name)
}
function Child() {
}
//主要精髓所在
Child.prototype = new Parent()
Child.prototype.constructor = Child
var arzhChild = new Child()
arzhChild.getName() // 'arzh'

原型鏈繼承缺點(diǎn):

1.每個(gè)實(shí)例對(duì)引用類型屬性的修改都會(huì)被其他的實(shí)例共享

function Parent() {
    this.names = ['arzh','arzh1'];
}
function Child() {
}
//主要精髓所在
Child.prototype = new Parent()
Child.prototype.constructor = Child
var arzhChild2 = new Child()
arzhChild2.names.push('arzh2')
console.log(arzhChild2.names) //[ 'arzh', 'arzh1', 'arzh2' ]
var arzhChild3 = new Child()
arzhChild3.names.push('arzh3')
console.log(arzhChild3.names) //[ 'arzh', 'arzh1', 'arzh2', 'arzh3' ]

2.在創(chuàng)建Child實(shí)例的時(shí)候，無法向Parent傳參。這樣就會(huì)使Child實(shí)例沒法自定義自己的屬性（名字）

借用構(gòu)造函數(shù)(經(jīng)典繼承)

function Parent() {
    this.names = ['arzh','arzh1']
}
function Child() {
    Parent.call(this)
}
var arzhChild2 = new Child()
arzhChild2.names.push('arzh2')
console.log(arzhChild2.names) //[ 'arzh', 'arzh1', 'arzh2' ]
var arzhChild3 = new Child()
arzhChild3.names.push('arzh3')
console.log(arzhChild3.names) //[ 'arzh', 'arzh1', 'arzh3' ]

優(yōu)點(diǎn):

解決了每個(gè)實(shí)例對(duì)引用類型屬性的修改都會(huì)被其他的實(shí)例共享的問題
子類可以向父類傳參

function Parent(name) {
    this.name = name
}
function Child(name) {
    Parent.call(this, name)
}
var arzhChild = new Child('arzh');
console.log(arzhChild.name); // arzh
var arzhChild1 = new Child('arzh1');
console.log(arzhChild1.name); // arzh1

缺點(diǎn):

無法復(fù)用父類的公共函數(shù)
每次子類構(gòu)造實(shí)例都得執(zhí)行一次父類函數(shù)

組合式繼承(原型鏈繼承和借用構(gòu)造函數(shù)合并)

function Parent(name) {
    this.name = name
    this.body = ['foot','hand']
}
function Child(name, age) {
    Parent.call(this, name)
    this.age = age
}
Child.prototype = new Parent()
Child.prototype.constructor = Child
var arzhChild1 = new Child('arzh1', '18')
arzhChild1.body.push('head1')
console.log(arzhChild1.name,arzhChild1.age) //arzh1 18
console.log(arzhChild1.body) //[ 'foot', 'hand', 'head1' ]
var arzhChild2 = new Child('arzh2', '20')
arzhChild2.body.push('head2')
console.log(arzhChild2.name,arzhChild2.age) //arzh2 20
console.log(arzhChild2.body) //[ 'foot', 'hand', 'head2' ]

優(yōu)點(diǎn):

解決了每個(gè)實(shí)例對(duì)引用類型屬性的修改都會(huì)被其他的實(shí)例共享的問題
子類可以向父類傳參
可實(shí)現(xiàn)父類方法復(fù)用

缺點(diǎn):

需執(zhí)行兩次父類構(gòu)造函數(shù)，第一次是Child.prototype = new Parent(),第二次是Parent.call(this, name)造成不必要的浪費(fèi)

原型式繼承

復(fù)制傳入的對(duì)象到創(chuàng)建對(duì)象的原型上，從而實(shí)現(xiàn)繼承

function createObj(o) {
    function F(){}
    F.prototype = o;
    return new F();
}
var person = {
    name : 'arzh',
    body : ['foot','hand']
}
var person1 = createObj(person)
var person2 = createObj(person)
console.log(person1) //arzh
person1.body.push('head') 
console.log(person2) //[ 'foot', 'hand', 'head' ]

缺點(diǎn): 同原型鏈繼承一樣，每個(gè)實(shí)例對(duì)引用類型屬性的修改都會(huì)被其他的實(shí)例共享

寄生式繼承

我們可以使用Object.create來代替上述createObj的實(shí)現(xiàn)，原理基本上是一樣的。寄生式繼承其實(shí)就是在createObj的內(nèi)部以某種形式來增強(qiáng)對(duì)象（這里的增強(qiáng)可以理解為添加對(duì)象的方法），最后返回增強(qiáng)之后的對(duì)象。

function createEnhanceObj(o) {
    //代替原型式繼承的createObj
    var clone = Object.create(o)
    clone.getName = function () {
        console.log('arzh')
    }
    return clone;
}

通過createEnhanceObj就可以在創(chuàng)建對(duì)象的時(shí)候，把對(duì)象方法也通過此種方式繼承。

缺點(diǎn): 同借用構(gòu)造函數(shù)一樣，無法復(fù)用父類函數(shù)，每次創(chuàng)建對(duì)象都會(huì)創(chuàng)建一遍方法

寄生組合式繼承

不需要為了子類的原型而多new了一次父類的構(gòu)造函數(shù)，如Child.prototype = new Parent() 只需要復(fù)制父類原型的一個(gè)副本給子類原型即可

function inheritPrototype(Parent, Child){
	Child.prototype = Object.create(Parent.prototype) //創(chuàng)建父類原型的一個(gè)副本,把副本賦值給子類原型
	Child.prototype.constructor = Child;
}
function Parent(name) {
    this.name = name
}
Parent.prototype.getName = function () {
    console.log(this.name)
}
function Child(color) {
    Parent.call(this, 'arzh')
    this.color = color
}
inheritPrototype(Parent, Child)
var arzhChild = new Child('red')
console.log(arzhChild.name) // 'arzh'

優(yōu)點(diǎn): 不必為了指定子類型的原型而調(diào)用父類型的構(gòu)造函數(shù)

ES6繼承

ES6支持通過類來實(shí)現(xiàn)繼承，方法比較簡(jiǎn)單，代碼如下

class Point {
    constructor(x, y) {
        this.x = x
        this.y = y
    }
    toString() {
        return this.x + '' + this.y
    }
}
class ColorPoint extends Point {
    constructor(x, y, color) {
        super(x, y) //調(diào)用父類的constructor(x, y)
        this.color = color
    }
    toString() {
        return this.color + ' ' + super.toString() // 調(diào)用父類的toString()
    }
}
var colorPoint = new ColorPoint('1', '2', 'red')
console.log(colorPoint.toString())  // red 12