function binarySearch(arr, item, start, end) { if (start > end) { return -1; } let mid = Math.floor((start + end) / 2); console.log(arr[mid]); // 用于打印被比较的数值 if (item === arr[mid]) { return mid; } else if (item < arr[mid]) { return binarySearch(arr, item, start, mid - 1); } else { return binarySearch(arr, item, mid + 1, end); } }