常用ES6特性

• 用let 来代替var即可，let定义不具有变量提升作用，同一作用域内不可重复定义，块级作用域

• const表示常量初始化后不可被修改，初始化必须被赋值，一旦初始化之后不可被改变

• class 和 extends

class base {    
  constructor(name) {      
  this.name = name;   
 };   
 say() {        
  console.log(this.name);   
 }
}
class thread extends base {   
 constructor(name, age) {      
  super(name);   
     this.age = age;  
  }   
 say() {  
      console.log(this.name, this.age);    
  }
}

• 字符串模板

console.log(`abcd${this.e}`)

• 默认参数

function say(name='Lyf',age=22){
console.log(name,age);
}
say('mx');

• 箭头函数，定义时就绑定不会被上下文环境改变，其值取决于父环境中this

o={
name:'name',
out1:function(){console.log(this.name)},
out2:()=>{console.log(this.name)}
}
o.out1()//name
o.out2()//undefined

(function () {
    name = 'quanjubianliang';
    var o = {
        name: 'name',
        out1: function () {
            console.log(this.name)
        },
        out2: ()=> {
            console.log(this.name)
        }
    };
    o.out1();//quanjubianliang
    o.out2();//name
})()

var oo = function () {
    this.name = 'name';
    this.out1 = function () {
        console.log(this.name)
    };
    this.out2 = ()=> {
        console.log(this.name)
    }
};
new oo().out1.call({name:'test'})//test
new oo().out2.call({name:'test'})//name

• 解构

var [x,y,z]=[1, 2];
var person = {firstName: "John", lastName: "Doe"};
var {firstName, lastName} = person;
console.log(firstName,lastName);