Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

var lengthOfLongestSubstring = function(s) {
  // Assign i to 0 to track index of s
  // Assign count to [ 0 ] to track lengths of all substrings
  // Assign start to 0 to track the beginning idx of a new substring

  // Iterate over s while i < s.length
    // If slice of s from start to i does not include the current char at i of s
      // Add 1 to the last element of the count array
      // Add 1 to i
    // Else
      // Add a new length of 0 to last element of count array
      // Assign start and i to the previous index where the char at i of s appeared and then add 1

  // return the largest number within the count array
}

var lengthOfLongestSubstring = function(s) {
  let start = 0
  let i = 0
  let count = [ 0 ]

  while (i < s.length) {
    if (!s.slice(start, i).includes(s.charAt(i))) {
      count[count.length - 1]++
      i++
    } else {
      count[count.length] = 0
      start, i = s.slice(0, i).lastIndexOf(s.charAt(i)) + 1
    }
  }

  return count.reduce((max, current) => current > max ? current : max)
}