Style aus Stylesheet verändern#

    function findStyle(selectorText) {
      for (var i = 0; i < document.styleSheets.length; ++i) {
        var styleSheet = document.styleSheets[i];
        var css = styleSheet.cssRules || styleSheet.rules;
        for (var j = 0; j < css.length; ++j) {
          var rule = css[j];
          if (rule.selectorText == selectorText)
            return rule.style;
        }
      }
    }

Die Funktion kann dann wie folgt verwendet werden:

findStyle('.test').width = '100px';