一击孩、繼承

1、ES5 實現(xiàn)繼承

var Car = function (color, name, model) {
    this.color = color
    this.name = name
    this. model = model
    this.print = function () {
        console.log('My car is ' + this.color + ' ' +this.name + ' ' +this. model)
    }
}

var myCar = function (color, name, model) {
     Car.call(this, color, name, model)
}

myCar.prototype = Object.create(Car.prototype)

var myAudi = new myCar('red', 'Audi', 'A4L')
myAudi.print()  // My car is red Audi A4L

2鹏漆、ES6 實現(xiàn)繼承

class Car {
    constructor (color, name, model) {
        this.color = color
        this.name = name
        this. model = model
    }

    print () {
        console.log(`My car is ${this.color}  ${this.name}  ${this.model}`)
    }
}

class MyCar extends Car {   // 通過extends實現(xiàn)繼承
    constructor (color, name, model, price) {
        super(color, name, model)  // 實例化子類的時候把子類的數(shù)據(jù)傳給父類
        this.price = price
    }

    getPrice () {
        console.log(`My car's price is  ${this.price}`)
    }
}

let myAudi = new MyCar('white', 'Audi', 'A4L', '$35000')
myAudi.getPrice()  // My car's price is $35000
myAudi.print()  // My car is white  Audi  A4L

二巩梢、單例模式的實現(xiàn)

單例就是保證一個類只有一個實例，實現(xiàn)的方法一般是先判斷實例存在與否艺玲，如果存在直接返回括蝠，如果不存在就創(chuàng)建了再返回，這就確保了一個類只有一個實例對象饭聚。在JavaScript里忌警，單例作為一個命名空間提供者，從全局命名空間里提供一個唯一的訪問點來訪問該對象秒梳。

單例模式的核心：保證一個類僅有一個一個實例法绵，并提供一個訪問它的全局訪問點箕速。

1、ES5的單例模式寫法

var Car = function (color, name, model) {
    this.color = color
    this.name = name
    this. model = model
    this.instance = null
    this.print = function () {
        console.log('My car is ' + this.color + ' ' +this.name + ' ' +this. model)
    }
}

Car.getInstance = function(color, name, model) {
    if(!this.instance) {
        this.instance = new Car(color, name, model);
    }
    return this.instance;
}

var Audi = Car.getInstance('red','Audi', 'A4');
var Benz = Car.getInstance('white', 'Benz', 'C200');
Audi.print()  // My car is red Audi A4
Benz.print() // My car is red Audi A4

說明Audi和Benz指向的是唯一實例化的對象

2礼烈、ES6的單例模式寫法

class Car {
    constructor (color, name, model) {
        this.color = color
        this.name = name
        this. model = model
        console.log('實例化會觸發(fā)構(gòu)造函數(shù)')
        this.getCarInfo()
         this.instance = null
    }

    static getInstance (color, name, model) {
        if (!this.instance) {
            this.instance = new Car(color, name, model)
        }
        return this.instance
    }

    print () {
        console.log(`My car is ${this.color}  ${this.name}`)
    }

    getCarInfo () {
        console.log(`My car is ${this.color}  ${this.name}  ${this.model}`)
    }
}

let myCar1 = Car.getInstance('red', 'Benz', 'C200L')
let myCar2 = Car.getInstance('white', 'Benz', 'E200L')
let myCar3 = Car.getInstance('black', 'Benz', 'C200L')
let myCar4 = Car.getInstance('graw', 'Benz', 'E200L')
// 只打印第一次
// 實例化會觸發(fā)構(gòu)造函數(shù)
// My car is red  Benz  C200L

myCar1.print()
myCar2.print()
myCar3.print()
myCar4.print()
// 會打印4次
// My car is red  Benz
//  My car is red  Benz
// My car is red  Benz
// My car is red  Benz