如何计算嵌套数组中的项？

function calculateNestedArraySum(arr) {
  let sum = 0;
  for (let i = 0; i < arr.length; i++) {
    if (Array.isArray(arr[i])) {
      sum += calculateNestedArraySum(arr[i]);  // 递归调用
    } else {
      sum += arr[i];
    }
  }
  return sum;
}

const nestedArray = [1, 2, [3, 4, [5, 6]]];
const sum = calculateNestedArraySum(nestedArray);
console.log(sum);  // 输出: 21

function calculateNestedArraySum(arr) {
  let sum = 0;
  const stack = [...arr];
  
  while (stack.length) {
    const item = stack.pop();
    if (Array.isArray(item)) {
      stack.push(...item);
    } else {
      sum += item;
    }
  }
  
  return sum;
}