连接

• concat(): 连接两个或多个数组

• join(): 将数组元素连接成字符串

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

let joinedString = arr1.join('-'); // '1-2-3'