binarySearch.js

function binarySearch(array, start, end, target) {
  while (true) {
    if (start > end) return -1;
    if (end - start < 2) {
      if (target === array[end]) return end;
      else if (target === array[start]) return start;
      else return -1;
    }
    var mid = Math.floor((start + end) / 2);
    if (target === array[mid]) return mid;
    else if (target < array[mid]) end = mid;
    else start = mid + 1;
  }
}