Javascript Film Grain Effect Help

All I wanna do is learn how to recreate this film grain effect:

I tried recreating it in webflow but no luck. What am i missing :face_with_monocle:

Webflow:
https://preview.webflow.com/preview/js-playful?utm_source=js-playful&preview=cb46733e4f927794f6f7eabe597a3e6e

Live:
https://js-playful.webflow.io/

suspicious thinking GIF by SpongeBob SquarePants