title: How to preload large css and javascript files in vanilla javascript
body: <p>I'm building a single page application that's going to run on tablets in areas of the world that have slow connections with poor bandwidth. </p>
  
  <p>Because the javascript files and css files are quite big, the css file is 250kb and the main js file is 750kb at the moment, I'm looking for a best practice to preload the css and javascript files without having to first load libraries such as JQuery first.</p>
  
  <p>So in short: What is a good way to preload css and js files without 3rd party libraries and have some sort of callback once all the files are loaded</p>