How does the Gmail unsubscribe button work?
How exactly does the Gmail unsubscribe button work and how can you make sure it always shows for your mailing-list emails?

https://www.chosenplaintext.ca/articles/radix-2-51-trick.html

Frameworkless Movement
Frameworkless movement

https://evertpot.com/ecmascript-4-the-missing-version/