code: function(str, filter, style) {
    // determine length
    var len;
    if (filter.isExpandable) {
      len = filter.getMatchLen(str);
    } else {
      len = filter.word.length;
    }
    // generate grawlix
    if (!style.canRandomize()) {
      return style.getFillGrawlix(len);
    }
    return style.getRandomGrawlix(len);
  }
docs: Replaces matched content with a grawlix, taking into account filter and style
  settings.
  @param  {String}        str       Content string
  @param  {GrawlixFilter} filter    Filter object
  @param  {GrawlixStyle}  style     Style object
  @return {String}                  Grawlix replacement string