JS 这个题目怎么写啊 求助各位大佬！

JS 这个题目怎么写啊 求助各位大佬！

    function onload() {
        var arr = getArr();
        var i = binary_search(arr, 17711);
        console.log(i);
    }

    function binary_search(array, value) {
        var left = 0;
        var right = array.length - 1;

        while (left <= right)
        {
            var middle = left + ((right - left) >> 1);

            if (array[middle] > value)
            {
                right = middle-1;
            }
            else if(array[middle] < value)
            {
                left = middle + 1;
            }
            else
                return middle;
        }
        return -1;
    }

    function getArr () {
        var a = 0;
        var b = 1;
        var arr = [];
        for (var i = 0; i < 30; i++) {
            arr[i] = a + b;
            a = b;
            b = arr[i];
        }
        return arr;
    }

 

就是没输出结果

是个空白的