Load those scripts all async like!

loadscripts.js

// TODO: convert into promise =)

// Load Script
function loadScript(url, callback) {
  if (!url || url === '') return;

  var scriptElement = document.createElement('script');
  scriptElement.src = url;

  if(typeof callback === 'function') {
    scriptElement.onload = callback;
  }

  document.body.insertAdjacentElement('beforeend', scriptElement);
}

// Load Script Files
/*
 * Expects array of objects in the format:
 * {
 *   url: 'path/to/script.js',
 *   callback: function () {}
 * }
 *
 * The callback is optional.
 *
 */
function loadScripts(scripts, complete) {
  if (scripts.length > 0) {
    scripts.forEach(function(script) {
      loadScript(script.url, script.callback);
    });

    if (typeof complete === 'function') {
      complete();
    }
  }
}