Dynamically load a JS or CSS file

Dynamic-Load-JS-CSS-Resource.js

function LoadResource(url, afterUi) {
   var
      p = new $.Deferred(),
      resource = null,
      headOrBody = document.getElementsByTagName(typeof afterUi !== 'undefined' && afterUi ? "body" : "head")[0];
   if (url.match(/.js$/gi)) {
      resource = document.createElement("script");
      resource.type = "text/javascript";

      if (resource.readyState) { // IE
         resource.onreadystatechange = function() {
            if (resource.readyState == "loaded" || resource.readyState == "complete") {
               resource.onreadystatechange = null;
               p.resolve(url);
            }
         };
      } else { // good browsers
         resource.onload = function() {
            resource.onload = null;
            p.resolve(url);
         };
      }
      resource.src = url;
   } else if (url.match(/.css$/gi)) {
      resource = document.createElement('link');
      resource.rel = 'stylesheet';
      resource.type = "text/css";
      resource.href = url;
      p.resolve(url);
   }
   if (resource) {
      headOrBody.appendChild(resource);
   } else {
   	p.reject('unsupported resource type, only *.js or *.css are allowed!');
   }
   return p.promise();
}