JS中二分法查找元素

  var arr = [1,2,4,5,77,333,451,767]
        function searching(target){
            //声明要使用的变量
            var start =0,end =arr.length-1,middle,element;
            while(start <= end){
                //确定中间值索引
                middle =Math.floor((start +end)/2);
                //给中间值赋值
                element = arr[middle];
                if( element === target){
                    return middle;
                }else if(target < element){
                    end = middle -1;
                }else if(target > element){
                    start = middle +1;
                }else{
                    return -1;
                }
            } 
        }