关于javascript:获取数组嵌套深度

   function getDeep(arr) {
            let flag = false;
            let num = [];
            for (let i = 0; i < arr.length; i++) {if (Array.isArray(arr[i])) {
                    flag = true;
                    num.push(getDeep(arr[i]));
                }
            }
            if (flag) {return Math.max(...num)+1
            } else {return 1}
         }