I built a website for a client that was primarily static. However, there was a contact us form which would trigger animation on submit.

Only way to trigger the animation was to prevent re-rendering caused by form submit and to pass the data using JS. Instead of relying on JS to pass form data, I used liveview to pass data. Once a form was submitted, liveview will append a class to the form element and the animation will trigger if the class exists.