擴展運算符（Spread operator）

let zzz=[2,4,6];
console.log(zzz);//[2, 4, 6]
console.log(...zzz);//2 4 6

展開併合並

let a=[1,2,3];
let b=[...a,4,5,6];
console.log(b);//1,2,3,4,5,6

let da=[1,2];
let db=Array.from(da);
db.push(3);
console.log(da,db);//[1, 2]   [1, 2, 3]

concat的連接數組

var arr5= [3,4,5]
    var arr6 = [6,7,8]
    var arr7 = arr5.concat(arr6);
    console.log(arr7);//3,4,5,6,7,8
    var arr8 = [...arr5,...arr6];
    console.log(arr8);//3,4,5,6,7,8

將字元串轉化成數組

var str = 'html';
var arr9 = [...str];
console.log(arr9);//["h", "t", "m", "l"]

應用在解構賦值里

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

var aa=[1,2,3];
var bb=[...aa];
bb.push(4,5);
console.log(bb);//[1, 2, 3, 4, 5]

函數調用

function aa(a,b){
        return a+b
}
let cc=[1,3]
let bb=aa(...cc)
console.log(bb);//4