Add jQuery to any page that does not have it already.

addJquery.js

(function() {
  if ( !window.jQuery ) {
    var $inUse = !!window.$,
    script = document.createElement('script');
    
    script.setAttribute('src', '//ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js');
    
    script.addEventListener('load', function(){
      console.log('jQuery was loaded.');
      if ($inUse) {
        jQuery.noConflict();
        console.log('jQuery was loaded in noConflict mode, use jQuery instead \'$\' ');
      }
    });

    document.body.appendChild(s);
  }
})();