Added JavaScript and CSS files to page

add_script.js

function addScript(url) {
  var head, script;
  head = document.querySelector('head');
  script = document.createElement('script');
  script.type = 'text/javascript';
  script.src = url; head.appendChild(script);
};

function addStylesheet(url) {
  var head, link;
  head = document.querySelector('head');
  link = document.createElement('link');
  link.type = 'text/css';
  link.rel = 'stylesheet';
  link.href = url;
  head.appendChild(link);
}