lengthOfLongestSubstring.js

var lengthOfLongestSubstring = function(s) {
  // input: string (s)
  // output: num (longest non consecutive string length)
  
  const sArr = s.trim().split('');
  const map = new Map();
  let uniqueStr = '';
  let uniqueStrMax = 0;
 
  for (var i = 0; i < sArr.length; i++) {
   
    const letter = sArr[i];
    
    // there are no duplicates yet.
    if (map.has(letter)) {
     // there are duplicates now.
     // if there are duplicates, we don't want to set the temporary string anymore...We also want to reset the length of the uniqueStrMax if we need to.
     if (uniqueStr.length >= uniqueStrMax) {
       uniqueStrMax = uniqueStr.length;
     }
      
     let subStrStart = uniqueStr.indexOf(letter);
     uniqueStr = uniqueStr.substring(subStrStart + 1);
    }
 
    uniqueStr += letter;
    map.set(letter, i + 1);
  }
  
  if (uniqueStr.length >= uniqueStrMax) {
    uniqueStrMax = uniqueStr.length;
  }
  
  return uniqueStrMax;
};