// 非递归算法
  function binary_search(arr, key) {
   var low = 0,
    high = arr.length - 1;
   while(low <= high){
    var mid = parseInt((high + low) / 2);
    if(key == arr[mid]){
     return mid;
    }else if(key > arr[mid]){
     low = mid + 1;
    }else if(key < arr[mid]){
     high = mid -1;
    }else{
     return -1;
    }
   }
  };
  var arr = [1,2,3,4,5,6,7,8,9,10,11,23,44,86];
  var result = binary_search(arr,10);
  alert(result); // 9 返回目标元素的索引值  

 // 递归算法
  function binary_search(arr,low, high, key) {
   if (low > high){
    return -1;
   }
   var mid = parseInt((high + low) / 2);
   if(arr[mid] == key){
    return mid;
   }else if (arr[mid] > key){
    high = mid - 1;
    return binary_search(arr, low, high, key);
   }else if (arr[mid] < key){
    low = mid + 1;
    return binary_search(arr, low, high, key);
   }
  };
  var arr = [1,2,3,4,5,6,7,8,9,10,11,23,44,86];
  var result = binary_search(arr, 0, 13, 10);
  alert(result); // 9 返回目标元素的索引值