ES6

解构赋值

按照一定模式，可以从数组和对象中提取值，从而对变量进行赋值操作。

主要在数组和对象中执行解构赋值操作，下面罗列常用的情景操作。

 数组的解构赋值

基本使用：

var [a,b,c]=[1,2,3];
console.log(a) //1
console.log(b) //2
console.log(c) //3

如果解构不成功，左侧变量的值就会为undefined

var [a,b,c]=[1,3];
console.log(a) //1 
console.log(b) //3
console.log(c) //undefined

嵌套：

var [a,[[b],c]]=[1,[[2],3]];
console.log(a) //1
console.log(b)//2
console.log(c) //3

可忽略：

var [a,,c]=[1,2,3];
console.log(a) //1
console.log(c) //3

剩余运算符：

var [a,...b]=[1,2,3,4,5];
console.log(a) //1
console.log(b) //2,3,4,5

var [a,...b]=['A'];
console.log(a) //A
console.log(b) //[]

字符串：

var [a, b, c, d, e] = 'hello'
console.log(a) //h
console.log(b) //e
console.log(c) //l
console.log(d) //l
console.log(e) //o

默认值：

var [a = 1,b]=[2];
console.log(a) //2
console.log(b) //undefined

var [a = 1,b = 2]=[undefined,4];
console.log(a) //1
console.log(b) //4

对象的解构赋值

基本使用：

变量​必须与​属性​​同名​，才能取到正确的值，位置顺序没关系。

var { name, age } = { name: "sss", bar: "12" };
console.log(name) //sss
console.log(age) //undefined

嵌套：

var obj = {p:['tom',{age:'12'}]};
var {p:[QName,{age}]} = obj;
console.log(QName) //tom
console.log(age) //12

忽略：

var obj = {p:['tom',{age:'12'}]};
var {p:[,{age}]} = obj;
console.log(age) //12

剩余运算符：

var {a, b, ...rest} = {a: 10, b: 20, c: 30, d: 40};
console.log(a) //10
console.log(b) //20
console.log(rest) //{c:30 ,d:40}