Transate plugin with js & wp_localize_script

In your PHP you are localizing the script using wp_localize_script(). The way you’ve used it will create an object in JS named messageClip with the string as the copy property, but then in your JavaScript you’re not actually using this. In your JavaScript just get rid of const message etc. and use:

buttonclip.on('success', function(e){
    e.trigger.textContent = messageClip.copy;
});