Load CSS stylesheet or insert raw CSS dynamically with JavaScript.

JavaScript 'loadStyle' Dynamically

SDG = SDG || {};

SDG.loadStyle = function(cssSource, append) {
  var append = typeof append === 'undefined' ? true : append,
    external = !(cssSource.indexOf('{') > 0 && cssSource.indexOf('}') > 1),
    newElem = external ? ((function() {
      i = document.createElement('link');
      i.rel = 'stylesheet';
      i.href = cssSource;
      i.type = 'text/css';
      return i
    })()) : ((function() {
      i = document.createElement('style');
      i.type = 'text/css';
      i.innerHTML = cssSource;
      return i;
    })());


  var newCss = append ? document.querySelectorAll('html > * link:last-of-type,html > * style:last-of-type') : document.querySelectorAll('html > * link:first-of-type,html > * style:first-of-type');

  newCss = ((newCss.length > 0) ? (append ? newCss[newCss.length - 1] : newCss[0]) : (append ? document.querySelector('body > *:last-child') : document.querySelector('head > *:first-child')));

  newCss.insertAdjacentElement((append ? 'afterend' : 'beforebegin'), newElem);

};