function cssRuleListFor(cssRuleList, callback) { for (var n = 0; n < cssRuleList.length; n++) { var cssRule = cssRuleList[n]; if (cssRule instanceof CSSStyleRule) { callback(cssRule); } else if (cssRule instanceof CSSImportRule) { var cssStyleSheet = cssRule.styleSheet; cssRuleListFor(cssStyleSheet.cssRules || [], callback); } else if (cssRule instanceof CSSMediaRule) { Array.prototype.forEach.call(cssRule.media, function(media) { if (cssMediaQuery.match(media, SCREEN_CONFIG)) { cssRuleListFor(cssRule.cssRules || [], callback); } }); } } }