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);
