code: function getStylesheet(data, isUrl, cb) {
      var el = document.createElement(isUrl ? 'link' : 'style'),
          head = document.getElementsByTagName('head')[0];
  
      el.type = 'text/css';
  
      if (isUrl) {
        el.href = data;
        el.rel = 'stylesheet';
  
        // Waiting for script to load
        el.onload = el.onreadystatechange = function() {
          if ((!this.readyState ||
                this.readyState == 'loaded' ||
                this.readyState == 'complete')) {
            el.onload = el.onreadystatechange = null;
  
            if (typeof cb === 'function')
              cb();
          }
        };
      }
      else {
        el.innerHTML = data;
      }
  
      // Appending the stylesheet to head
      head.appendChild(el);
    }
docs: Loading an external stylesheet