ES6 ...

let arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];
let arr = [...arr1, ...arr2];
console.log(arr) // [ 1, 2, 3, 4, 5, 6 ]

concat

let arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];
arr = arr1.concat(arr2);
console.log(arr)// [ 1, 2, 3, 4, 5, 6 ]

push 结合 ...

let arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];
arr1.push(...arr2);
console.log(arr1) // [ 1, 2, 3, 4, 5, 6 ]

push 结合apply

let arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];
arr1.push.apply(arr1, arr2)
console.log(arr1) // [ 1, 2, 3, 4, 5, 6 ]