var script = document.createElement('script'); script.src = 'https://code.jquery.com/jquery-3.4.1.min.js'; script.type = 'text/javascript'; document.getElementsByTagName('head')[0].appendChild(script);
<head> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script> </head>
//add this line somewhere in the html <script src="http://code.jquery.com/jquery-1.11.0.min.js"></script>