Anime.js : Anime.js is a fast, multipurpose and lightweight JavaScript animation library with a simple, yet powerful API.
It works with CSS properties, SVG, DOM ...
Mousetrap : A simple library for handling keyboard shortcuts in Javascript.
Headroom.js : Headroom.js is a lightweight, high-performance JS widget (with no dependencies!) that allows you to react to the user's scroll.
Vanilla List : The Vanilla Javascript Repository. A searchable repository of dependency-free JavaScript libraries. Over 100 projects and growing.