es6中中展开运算符(...)

将字符串转成数组

var str="abcd";
console.log([...str]) // ["a", "b", "c", "d"]

将集合转成数组

var sets=new Set([1,2,3,4,5])
console.log([...sets]) // [1, 2, 3, 4, 5]

两个数组的合并

var a1=[1,2,3];
var a2=[4,5,6];
console.log([...a1,...a2]); //[1, 2, 3, 4, 5, 6]

在函数中，用来代替arguments参数
rest参数  …变量名称

rest 参数是一个数组 ，它的后面不能再有参数，不然会报错

function func(...args){
    console.log(args);//[1, 2, 3, 4]
}
func(1, 2, 3, 4);
 
function f(x, ...y) {
    console.log(x);
    console.log(y);
}
f('a', 'b', 'c');     //a 和 ["b","c"]
f('a')                //a 和 []
f()                   //undefined 和 []
 

• 移除某几项

    //数组
    const number = [1,2,3,4,5]
    const [first, ...rest] = number
    console.log(rest) //2,3,4,5
    //对象
    const user = {
        username: 'lux',
        gender: 'female',
        age: 19,
        address: 'peking'
    }
    const { username, ...rest } = user
    console.log(rest) //{"address": "peking", "age": 19, "gender": "female"