criando style e inserindo regras css

criando style e inserindo regras css

var sheet = (function() {
    // Create the <style> tag
    var style = document.createElement('style');
    // Add a media (and/or media query) here if you'd like!
    // style.setAttribute('media', 'screen')
    // style.setAttribute('media', 'only screen and (max-width : 1024px)')
    // WebKit hack :(
    style.appendChild(document.createTextNode(''));
    // Add the <style> element to the page
    document.head.appendChild(style);
    return style.sheet;
})();
// Usage
sheet.insertRule("header { float: left; opacity: 0.8; }", 1);