Make the Mailchimp Subscriber popup appear on click

clickable-element.html

<!-- This is the HTML element that, when clicked, will cause the popup to appear. -->

<button id="open-popup">Subscribe to our mailing list</button>

mailchimp_popup.js

<!-- this is not necessary if you're only adding popup-on-button functionality to already existing mailchimp popup.
     Also, mailchimp now uses something like //downloads.mailchimp.com/js/signup-forms/popup/unique-methods/2.0/popup.js
     with unique-methods in path which uses dojoRequire and dojoDefine instead of require and define
 -->
<script type="text/javascript" src="//s3.amazonaws.com/downloads.mailchimp.com/js/signup-forms/popup/embed.js" data-dojo-config="usePlainJson: true, isDebug: false"></script>

<script>
 function showMailingPopUp() {
           //  If your mailchimp popup tried loading automatically, but had a cookie and did not show
           //  If not done, close button would not work (sorry for jQuery)  -- basically removes previous popups
    $('[id^="PopupSignupForm"]').remove(); 	
           // clear 2 cookies on the root path
    document.cookie =     "MCPopupClosed=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/";
    document.cookie = "MCPopupSubscribed=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/";

   dojoRequire(         // using uniq methods, some older code may work with simple require
      ["mojo/signup-forms/Loader"], 
      function(L) { 
        L.start( {
          "baseUrl":"XXXX.usXX.list-manage.com",
          "uuid":"YOUR_USERID",
          "lid":"YOUR_FORM_ID",
          "uniqueMethods": true      // force using uniq methods inside, otherwise will complain about "require/define not defined"
        }); 
      });
  };

document.getElementById("open-popup").onclick = function() {showMailingPopUp()};
</script>