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. Hope it helps.

  function longestSubstringWithoutDuplication(str) {
      var max = 0;

      //if empty string
      if (str.length === 0){
        return 0;
      } else if (str.length === 1){ //case if the string's length is 1
        return 1;
      }

      //loop over all the chars in the strings
      var currentChar,
          map = {},
          counter = 0; //count the number of char in each substring without duplications
      for (var i=0; i< str.length ; i++){
        currentChar = str.charAt(i);

        //if the current char is not in the map
        if (map[currentChar]  == undefined){
          //push the currentChar to the map
              map[currentChar] = i;
              if (Object.keys(map).length > max){
                 max = Object.keys(map).length;
              }
        } else { //there is duplacation
          //update the max
          if (Object.keys(map).length > max){
            max = Object.keys(map).length;
          }
          counter = 0; //initilize the counter to count next substring
          i = map[currentChar]; //start from the duplicated char
          map = {}; // clean the map
        }
      }


     return max;
    }