const binarySearch = (array, key) => {
  let lo = 0,
      hi = array.length - 1,
      mid,
      element;
  while (lo <= hi) {
    mid = Math.floor((lo + hi) / 2, 10);
    element = array[mid];
    if (element < key) {
      lo = mid + 1;
    } else if (element > key) {
      hi = mid - 1;
    } else {
      return mid;
    }
  }
  return -1;
};