csslib.js

window.csslib = {
    createStyleSheet: function() {
        var el = document.createElement("style");
        el.appendChild(document.createTextNode(""));
        document.head.appendChild(el);
        return el.sheet;
    },
    
    addRule: function(sheet, selector, rules) {
        var ruleString = "";
        var keys = Object.keys(rules);
        
        for(var i = 0; i < keys.length; i++) {
            ruleString += keys[i] + ": " + rules[keys[i]] + "; ";
        }
                
        if(sheet.insertRule) {
            sheet.insertRule(selector + "{" + ruleString + "}", 0);
        }
        else if(sheet.addRule) {
            sheet.addRule(selector, ruleString, 0);
        }
    }
};