javascript-binarySearch

前提： 数组已排序，且为正整数数组.

 function brnarySearch(arg, arr) {
     var right = arr.length - 1;
     var left = 0;
     while(left <= right) {
           var mid = left + parseInt( (right - left) / 2 );
           if(arg < arr[mid]) right = mid - 1;
           else if(arg > arr[mid]) left = mid + 1;
           else return mid;
     }
     return -1;
 }
 var arr = [1, 3, 5, 7, 9, 11, 12, 44, 56];
 console.log(brnarySearch(9, arr));