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:

1.每個實例對引用類型屬性的修改都會被其他的實例共享

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實例的時候，無法向Parent傳參。這樣就會使Child實例沒法自定義自己的屬性（名字）

借用構造函數(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:

解決了每個實例對引用類型屬性的修改都會被其他的實例共享的問題
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:

無法復用父類的公共函數(shù)
每次子類構造實例都得執(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:

解決了每個實例對引用類型屬性的修改都會被其他的實例共享的問題
子類可以向父類傳參
可實現(xiàn)父類方法復用

缺點:

需執(zhí)行兩次父類構造函數(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

原型式繼承

復制傳入的對象到創(chuàng)建對象的原型上，從而實現(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: 同原型鏈繼承一樣，每個實例對引用類型屬性的修改都會被其他的實例共享

寄生式繼承

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

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)建對象的時候，把對象方法也通過此種方式繼承。

缺點: 同借用構造函數(shù)一樣，無法復用父類函數(shù)，每次創(chuàng)建對象都會創(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了一次父類的構造函數(shù)，如Child.prototype = new Parent() 只需要復制父類原型的一個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: 不必為了指定子類型的原型而調(diào)用父類型的構造函數(shù)

ES6繼承

ES6支持通過類來實現(xiàn)繼承，方法比較簡單，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