如何将数组插入数组中？

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

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

let arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];
for (let i = 0; i < arr2.length; i++) {
  arr1.push(arr2[i]);
}
console.log(arr1);