es6 解构赋值

结构赋值即按照一种模式对变量进行赋值，分为数组解构赋值和对象结构赋值

1. 数组结构赋值

let a;
[a,b]=[1,2]//数组类型解构赋值
console.log(a);//1


[a,b,...rest]=[1,2,3,4,5,6]//输出1,2,[3,4,5,6]


[a,b,c=3]=[1,2] //a=1,b=2,c=3

[a,b,c]=[1,2]//若左右没有配对成功，则会输出undefined。即c为undefined


let a=1;
let b=2;
[a,b]=[b,a];//可以进行交换，输出2,1


function f(){
    return [1,2]
}
let a,b;
[a,b]=f();//输出1,2


function f(){
    return [1,2,3,4,5]
}
let a,b,c;
[a,,,b]=f();//a,b输出1,4


function f(){
    return [1,2,3,4,5]
}
let a,b,c;
[a,...b]=f();//a,b输出1,[2,3,4,5]

2.对象解构赋值

let o={p:42,q:true} 
let {p,q}=o;//对象解构赋值左右都是对象
console.log(p,q);//42,true


let {a=10,b=5}={a:3};
console.log(a,b);//3,5


let metaData={
    title:"abc",
    test:[{
        title:"test",
        desc:"description"
    }]
}
let {title:esTitle,test:[{title:cnTitle}]}=metaData;
console.log(esTitle,cnTitle);//输出abc,test