剩余參數(shù)允許我們將一個(gè)不定數(shù)量的參數(shù)表示為一個(gè)數(shù)組。

function sum (first, ...args) {
   console.log(first);    //10
   console.log(args);  // [20,30]
}

sum(10, 20, 30)

const sum  = (...args) => {
  let total = 0;
  args.forEach(item => total += item);
  return total;
}

剩余參數(shù)和解構(gòu)賦值配合使用

let  students = ['王五'，'張三'，'李四'];
let [s1, ...s2] = students;
console.log(s1); //  '王五'
console.log(s2);  // [  '張三'，'李四' ]

擴(kuò)展運(yùn)算符

擴(kuò)展運(yùn)算符可以將數(shù)組或者對(duì)象轉(zhuǎn)為用逗號(hào)分隔的參數(shù)序列。

let ary = [1, 2, 3];
...ary  // 1, 2, 3

擴(kuò)展勻運(yùn)算符 可以應(yīng)用于合并數(shù)組

let ary1 = [1, 2,  3];
let ary2 = [4, 5,  6];
let ary3 = [...ary1, ...ary2]
// 防法2
ary1.push(...ary2);

將類數(shù)組或可遍歷對(duì)象轉(zhuǎn)換為真正的數(shù)組

 <div>1</div>
 <div>2</div>
 <div>3</div>
 <div>4</div>
 <div>5</div>

var oDivs = document.getElementsByTagName('div');
console.log(oDivs)
var  ary = [... oDivs];
ary.push('a');
console.log(ary)