I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.
You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.
If you have your JS code in a separate file, you can’t add an event listener to your button like you’re currently doing. You have to add it within your script file instead: