code: function createAlwaysStylePattern(markers, exceptions) {
      let pattern = "^";
  
      /*
       * A marker or nothing.
       * ["*"]            ==> "\*?"
       * ["*", "!"]       ==> "(?:\*|!)?"
       * ["*", "/", "!<"] ==> "(?:\*|\/|(?:!<))?" ==> https://jex.im/regulex/#!embed=false&flags=&re=(%3F%3A%5C*%7C%5C%2F%7C(%3F%3A!%3C))%3F
       */
      if (markers.length === 1) {
  
          // the marker.
          pattern += escape(markers[0]);
      } else {
  
          // one of markers.
          pattern += "(?:";
          pattern += markers.map(escape).join("|");
          pattern += ")";
      }
  
      pattern += "?"; // or nothing.
      pattern += createExceptionsPattern(exceptions);
  
      return new RegExp(pattern, "u");
  }
docs: Creates RegExp object for `always` mode.
  Generated pattern for beginning of comment:
  
  1. First, a marker or nothing.
  2. Next, a space or an exception pattern sequence.
  
  @param {string[]} markers - A marker list.
  @param {string[]} exceptions - An exception pattern list.
  @returns {RegExp} A RegExp object for the beginning of a comment in `always` mode.