1. Array.prototype.binarySearch = function(item) {
    2.     let low = 0;
    3.     let high = this.length - 1;
    5.     while(low <= high) {
    6.         const mid = Math.floor((low + high) / 2);
    7.         const element = this[mid];
    9.         if(element < item) {
    10.             low = mid + 1
    11.         } else if (element > item) {
    12.             high = mid - 1
    13.         } else {
    14.             return mid
    15.         }
    16.     }
    17.     return -1
    18. }
    20.   const res = [1, 2, 3, 4, 5].binarySearch(3);
    21.   console.log(res);

    时间复杂度：O（logN）