Find longest substring without repeating characters

Question

Given a string S of length N find longest substring without repeating characters.

Example:

Input:

Answer 1

This is my solution, and it was accepted by leetcode. However, after I saw the stats, I saw whole lot solutions has much faster result....meaning, my solution is around 600ms for all their test cases, and most of the js solutions are around 200 -300 ms bracket.. who can tell me why my solution is slowwww??

var lengthOfLongestSubstring = function(s) {
  var arr = s.split("");

  if (s.length === 0 || s.length === 1) {
    return s.length;
  }

  var head = 0,
    tail = 1;
  var str = arr[head];
  var maxL = 0;
  while (tail < arr.length) {
    if (str.indexOf(arr[tail]) == -1) {
      str += arr[tail];
      maxL = Math.max(maxL, str.length);
      tail++;
    } else {
      maxL = Math.max(maxL, str.length);
      head = head + str.indexOf(arr[tail]) + 1;
      str = arr[head];
      tail = head + 1;
    }
  }
  return maxL;
};