vanilla js getScript.js

function getScript(url, callback, timeout) {
  var timeoutIdx,
    s = document.createElement('script');

  s.type = 'text/' + (url.type || 'javascript');
  s.src = url.src || url;
  s.async = false;

  s.onreadystatechange = s.onload = function() {
    // this code handles two scenarios, whether called by onload or onreadystatechange
    var state = s.readyState;

    clearTimeout(timeoutIdx);

    if (!callback.done && (!state || /loaded|complete/.test(state))) {
      callback.done = true;
      callback();
      s.onreadystatechange = s.onload = null;
    }
  };

  document.body.appendChild(s);

  // You can't catch JSONP Errors, because it's handled by the script tag
  // one way is to use a timeout
  timeoutIdx = setTimeout(function() {
    callback.done = true;
    callback();
    s.onreadystatechange = s.onload = null;
  }, timeout);
}