解构赋值

1、非常有用，特别在做数据交互 ajax

let [a,b,c] = [12,4,5]

注意：左右两边的结构要保持一致

2、json:

 let json = {
      name:'fanfan',
      age:19,
      sex:'max'
}
let{name,age,sex}=json
console.log(name,age,sex)

3、解构时候可以给默认值：

 let [a,b,c="默认值"] = ['aaa','bbb'] 

4、计算参数之和

function sum(...num){
    var sumNum = 0;
    for(let i=0;i<num.length;i++){
        sumNum += parseInt(num[i])
    }
    console.log(sumNum)
 }

sum(1,2,3)      //6
sum(1,2,"3")     //6
sum(1,3,"6和4")   //10

function Sum(...nums){
  let sum = nums.reduce((x,y)=>{return x+y})
  return sum
}