code: function isAlphaNumericAt(str, i)
  {
      var code = str.charCodeAt(i);
      //        "0" <= code <= "9"           "A" <= code <= "Z"         "a" <= code <= "z"
      return ((code > 47 && code < 58) || (code > 64 && code < 91) || code > 96 && code < 123);
  }
docs: Determine if the character at position i is in [a-zA-Z0-9]
  @param {String} str
  @param {Number} i
  @return {Boolean}