javascript二分查找

/*
二分查找(折半查找)
思路:
low和high表示下标，选择每个数组的中点作为基准，比较基准与key的值，
若大于基准，则移动low，反之移动high，等于则返回该值，不存在返回-1
遇到的问题：写成了死循环，无返回值

*/
var arr = [1,4,5,7,3,9,8];
var ff = binarySearch(arr,4);

console.log(ff);

function binarySearch(arr,key) {
    var low = 0;
    var high = arr.length-1;

    while(low<=high){
        var mid =Math.floor( (high+low)/2);
        if(arr[mid]==key){
        return arr[mid];
    }
        if (key<arr[mid]) {
            high = mid;
        }else if(key>arr[mid]){
            low = mid;
        }else{
            return mid;
        }
    }

     return -1;

}