let foo = ["a","b","c"]

let [a,b] = foo; // a = "a" ; b = "b"

class A{
constructor(name,age){
this.name = name;
this.age = age
}
}

//
class B extends A{
constructor(){
// 子类必须在constructor 中指定super 函数
// 如果没有置顶constructor 默认带super的函数的constructor 将会被添加
super("lxy",25)
}
}

export const a = "123"


export default {

}

import A from "a" // a.js

let c = "c"

let b = `ab ${a}` // abc

const a = "a"
const b = "b"

const c = {
a:a
b:b
}

// 简写

const c = {
a,
b
}

let req = new Promise((resolve,reject)=>{
setTimeout(resolve,1000)
})

req.then(res => {
console.log(res)
})