lengthOfLongestSubstring.js

var lengthOfLongestSubstring = function(s) {
  var longStr = '', curStr = '';
  var strArr = s.split('');

  for (var i = 0; i < strArr.length; i++) {
    if (curStr.indexOf(strArr[i]) == -1) {
      curStr += strArr[i];
    } else {
      idx = curStr.indexOf(strArr[i]);
      curStr = curStr.slice(idx+1);
      curStr += strArr[i];
    }

    if (curStr.length > longStr.length) {
      longStr = curStr;
    }
  }
  return longStr.length;
};




var lengthOfLongestSubstring2 = function(s) {
      var longStr = '', curStr = '';
      var strArr = s.split('');

      for (var i = 0; i < strArr.length; i++) {
        var idx = curStr.indexOf(strArr[i]);
        if (idx !== -1) {
          curStr = curStr.slice(idx+1);
        }
        curStr += strArr[i];

        if (curStr.length > longStr.length) {
          longStr = curStr;
        }
      }
      return longStr.length;
};

性能上的差异还不小， 要一探究竟