JS实现的算法（八）--二分查找

var arr = [1, 4, 5, 6, 12, 43, 111];
function search(arr, l, h, num) {
  var mid = Math.floor((l + h) / 2);
  if (l > h) {
    return -1;
  }
  if(arr[mid] === num) {
    return mid;
  }
  if(arr[mid] > num) {
    h = mid - 1;
    return search(arr, l, h, num);
  }
  if(arr[mid] < num) {
    l = mid + 1;
    return search(arr, l, h, num);
  }
}