Manipulating CSS pseudo-elements using jQuery

jquery.addrule.js

/*!
   * jquery.addrule.js 0.0.1 - https://gist.github.com/yckart/5563717/
   * Add css-rules to an existing stylesheet.
   *
   * @see http://stackoverflow.com/a/16507264/1250044
   *
   * Copyright (c) 2013 Yannick Albert (http://yckart.com)
   * Licensed under the MIT license (http://www.opensource.org/licenses/mit-license.php).
   * 2013/05/12
   **/

  (function ($) {
    window.addRule = function (selector, styles, sheet) {
      if (typeof styles !== "string") {
        var clone = "";
        for (var style in styles) {
          var val = styles[style];
          style = style.replace(/([A-Z])/g, "-$1").toLowerCase(); // convert to dash-case
          clone += style + ":" + (style === "content" ? '"' + val + '"' : val) + "; ";
        }
        styles = clone;
      }
      sheet = sheet || document.styleSheets[0];
      sheet.addRule(selector, styles);
      return this;
    };
    if ($) {
      $.fn.addRule = function (styles, sheet) {
        addRule(this.selector, styles, sheet);
        return this;
      };
    }
  }(window.jQuery));