JavaScript:如何通过`forEach`或`for`循环返回修改后的函数？

const arr = [1, 2, 3, 4, 5];

arr.forEach((num, index, array) => {
  array[index] = num * 2;
});

console.log(arr); // 输出 [2, 4, 6, 8, 10]

const arr = [1, 2, 3, 4, 5];

for (let i = 0; i < arr.length; i++) {
  arr[i] = arr[i] * 2;
}

console.log(arr); // 输出 [2, 4, 6, 8, 10]