defer.js

var _scripts = [
  '/vendor/javascripts/jquery.js',
  '/vendor/javascripts/moment.js',
  '/vendor/javascripts/mixpanel.js',
  '/javascripts/main.js'
];

(function (scripts) {
  'use strict';
  function downloadJSAtOnload() {
    if (!scripts.length) {
      return;
    }
    var element = document.createElement("script");
    element.src = scripts.shift();
    element.onload = element.onreadystatechange = function () {
      if (!this.readyState || this.readyState === 'loaded' || this.readyState === 'complete') {
        downloadJSAtOnload();
      }
    };
    document.body.appendChild(element);
  }
  if (window.addEventListener) {
    window.addEventListener("load", downloadJSAtOnload, false);
  } else if (window.attachEvent) {
    window.attachEvent("onload", downloadJSAtOnload);
  } else {
    window.onload = downloadJSAtOnload;
  }
})(_scripts);