Attempting to follow http://demos.jquerymobile.com/1.4.0/collapsible/ article

Attempting to follow http://demos.jquerymobile.com/1.4.0/collapsible/ article

This is my code. Something is missing because the icon with the + sign does not appear. Also the content is shown by default, rather than closed as specified in the text. Is there anything else I need to add to this code:

  1. <!DOCTYPE html>
    <html>
    <head>
      <link rel='stylesheet' href='jquery/mobile/jquery-mobile-1.4.5.css' type='text/css'>
    </head>
    <body>
      <div data-role="collapsible">
        <h4>Heading</h4>
        <p>I'm the collapsible content. By default I'm closed, but you can click the header to open me.</p>
        <input id='btnClick' type='button' value='click here' />
      </div>



    </body>
    </html>
    <script type='text/javascript' src='jquery/mobile/jquery-mobile-1.4.5.js'></script>
    <script type='text/javascript' src='jquery/jquery-1.12.4.js'></script>
    <script>
    $("#btnClick").on("click", function() {
      alert('jquery must be working!');
    });


    </script>