一.babel转换器:babel.js.io;

 

二.变量声明.

1.块级作用域let:

传统var声明: var a = [];for (var i = 0; i < 10; i++) {  a[i] = function () {    console.log(i);  };}a[6](); // 10 变量let声明：

var a = [];for (let i = 0; i < 10; i++) { a[i] = function () { console.log(i); }; } a[6](); // 6

2.常量const:一旦声明不可改变，一般用来引入模块，例如：const moment=require("moment");

 

三.类Class

class Animal {    constructor(){        this.type = 'animal'    }    says(say){        console.log(this.type + ' says ' + say)    }}let animal = new Animal()animal.says('hello') //animal says helloclass Cat extends Animal {    constructor(){        super()//指代父类的实例，必须要有。        this.type = 'cat'    }}let cat = new Cat()cat.says('hello') //cat says hello

 

四.箭头函数arrow function

1.简化写法

function(x, y) {     x++;    y--;    return x + y;}//es5(x, y) => {x++; y--; return x+y}//es6

2.使用箭头函数时，函数体内的this对象，就是定义时所在的对象，看例题：

class Animal {    constructor(){        this.type = 'animal'    }    says(say){        setTimeout(function(){            console.log(this.type + ' says ' + say)        }, 1000)    }} var animal = new Animal() animal.says('hi')  //undefined says hi,因为setTimeout中的this对象指向全局对象，在ES5中一般是把this赋值给常量然后代入，或者使用.bind(this)class Animal {    constructor(){        this.type = 'animal'    }    says(say){        setTimeout( () => {            console.log(this.type + ' says ' + say)        }, 1000)    }} var animal = new Animal() animal.says('hi')  //animal says hi

 

五.template string:简化拼接字符串写法

$("#result").append(  "There are " + basket.count + " " +  "items in your basket, " +  "" + basket.onSale +  " are on sale!");//es5中，使用拼接字符串形式$("#result").append(`  There are ${basket.count} items   in your basket, ${basket.onSale}  are on sale!`);//es6中，将字符串放在单引号内，变量则放在${}中

六.解构:destructuring:允许按照一定模式，从数组和变量中取得值，对变量进行赋值.

let cat = 'ken'let dog = 'lili'let zoo = {cat: cat, dog: dog}console.log(zoo)  //Object {cat: "ken", dog: "lili"},es5let cat = 'ken'let dog = 'lili'let zoo = {cat, dog}console.log(zoo)  //Object {cat: "ken", dog: "lili"},es6 反过来：

let dog = {
     type: 'animal', many: 2} let { type, many} = dog console.log(type, many) //animal 2

七.default默认值

function animal(type){    type = type || 'cat'      console.log(type)}animal()//es5function animal(type = 'cat'){    console.log(type)}animal()//es6

rest

function animals(...types){    console.log(types)}animals('cat', 'dog', 'fish') //["cat", "dog", "fish"]