code: function isValid(ch){
    var code = ch.charCodeAt(0);
    return is_letter(code)
      || is_digit(code)
      || (ch === '.')
      || (ch === '_')
      || is_unicode_connector_punctuation(ch)
      || is_unicode_format(ch)
      || is_unicode_combining_mark(ch)
      || is_unicode_digit(ch);  
  }
docs: Tests if the specified character is valid.
  @param {String} ch The character to test.
  @returns {Boolean} The