递归

    1. function binary_search(arr, low, high, key) {
    2.     if (low > high) {
    3.         return -1;
    4.     }
    5.     var mid = parseInt((high+low) / 2);
    6.     if (arr[mid] == key) {
    7.         return mid;
    8.     } else if (arr[mid] > key) {
    9.         high = mid - 1;
    10.         return binary_search(arr, low, high, key);
    11.     } else if (arr[mid] < key) {
    12.         low = mid   1;
    13.         return binary_search(arr, low, high, key);
    14.     }
    15. }

    非递归

    1. function binary_search(arr, key) {
    2.     var low = 0;
    3.     var high = arr.length - 1;//定义变量为数组两端的下标
    5.     while(low <= high) {
    6.         var mid = parseInt((high + low) /2);//步骤1
    7.           if(key == arr[mid]) {
    8.             return mid;//步骤2
    9.         } else if(key > arr[mid]) {
    10.             low = mid + 1;//步骤3
    11.         } else {
    12.             high = mid -1;//步骤4
    13.         }
    14.     }
    15.     return -1//步骤6
    16. }