ES6的新特性

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1.箭头函数 

var arr = [1,2,3];
        //传统写法 
arr.forEach( function(val, index) {
    console.log(index + ' ' + val+',')//0 1,1 2,2 3
});
        //es6
arr.forEach((val,index) => console.log(index + ' ' + val)); //0 1,1 2,2 3

2.类的支持

class People  {
    constructor(name='jack'){ //默认参数
        this.name = name; // this.name = name||'jack'传统默认参数
    }
    sayHello() {
        console.log(`my name is ${this.name}`) //字符串模版 反向‘
    }
}
class Student extends People{   //extends Es6 继承
    constructor(name) {
        super(name);
    }
    doSth() {
        console.log('I am doing homework')
    }
}
var noname = new Student();
var leonel = new Student('leonel');
noname.sayHello();//my name is jack
leonel.sayHello();//my name is leonel
leonel.doSth();//I am doing homework

3.解构

var  [x,y] = getVal(),
    [name,,sex]=['leonel',25,'man'];
function getVal() {
    return [0,1];
}
console.log('x:'+x+'   y:'+y)//x:0 y:1
console.log('name:'+name+'   sex:'+sex) //name:leonel  sex:man

4.不定参数

function print1(...x) { //...x 相当于arguments
    for(let v of x) {     //for of 遍历数组，类似于for in  区别：for in 遍历的是key,for of 遍历的是value
        console.log(v) 
    }
}
function print2(arguments) { //...x 相当于arguments
    for ( let i in arguments ){  //let 定义局部变量 只有 当前体内才能使用
        console.log(i)   
    }
    //console.log(i) //报错  i is undefined
}
var arr = ['one','two','three'];
print1(...arr) // one two three 
//传统写法print1('one','two','three')
print2(...arr) // 0  1 2 

5.Proxies

var enginner = {name: 'leonel',age:25}; //被监听的对象
var doProcess ={
    set:function(received,property,value){
        console.log(property +"  is changed");
        received[property] = value;
    }
}
enginner = new Proxy(enginner,doProcess); //new 一个proxy  doprocess 监听 enginner 上发生改变了什么
enginner.age=40; //age is changed

 6.Promise　

//创建promise
var promise = new Promise(function(resolve, reject) {
    // 进行一些异步或耗时操作
    if ( /*如果成功 */ ) {
        resolve("Stuff worked!");
    } else {
        reject(Error("It broke"));
    }
});
//绑定处理程序
promise.then(function(result) {
    //promise成功的话会执行这里
    console.log(result); // "Stuff worked!"
}, function(err) {
    //promise失败会执行这里
    console.log(err); // Error: "It broke"
})

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参考于博客ES6新特性概览、 阮老师的ECMAScript 6 入门