Creating a plugin to show a pop-up banner on every page

I used some javascript code to pop up the message, and placed it in my “Simple GDPR’ plugin https://wordpress.org/plugins/simple-gdpr/ .

I got the javascript code from https://cookieconsent.insites.com/ , which details how to do it.

I used the ‘after_header’ action , as in

add_action('after_header', 'my_gdpr_notice');

to display the notice, plus using the ‘enqueue_scripts‘ functions to add the javascript code and the associated CSS for the message.