rest参数

function test(a,b,...c){
    console.log(a);
    console.log(b);
    console.log(c);

}
test(1,2,3,4,5,6,7,8)
//1和2赋给了a,b 345678赋给了c(数组)
//传进来后面的参数会被当成数组添加到c里面
//也可以把参数改成一个对象,打印c object
//...表示不知道传进来多少个参数

作用

实现加法

`function test(...c) {
    let sum = 0;
    for(let i = 0; i < c.length; i++){
        sum += c[i];
    }
    console.log(sum);
}
test(1,2,3,4,5,6,7,8);//36

用在解构赋值里

数组

let a,b;
[a,...b] = [1,2,3,4,5,6,7,8];
console.log(a,b);
//b变成了数组2345678

字符串

let a,b;
[a,...b] = '123456789';
console.log(a,b)
//b数组["2","3","4","5","6","7","8","9"]