Granim.js
Create fluid and interactive gradients animations with this small (< 10 kB) js library.
Tippyjs
Highly customizable vanilla JS tooltip/popover library
Brain
[UNMAINTAINED] Neural networks in JavaScript
Vidage
Your solution to full-screen background video & image combined.
Stimulus
A modest JavaScript framework for the HTML you already have
Jimp
An image processing library written entirely in JavaScript for Node, with zero external or native dependencies.
Spectrum
The No Hassle JavaScript Colorpicker
Highland
High-level streams library for Node.js and the browser
Move.js
CSS3 backed JavaScript animation framework
Underscore String
String manipulation extensions for Underscore.js javascript library.
Redom
Tiny (2 KB) turboboosted JavaScript library for creating user interfaces.
Dynamics.js
Javascript library to create physics-based CSS animations
Proton
A particle engine for html5
Shipit
Universal automation and deployment tool written in JavaScript.
Imager.js
Responsive images while we wait for srcset to finish cooking
Choo
:steam_locomotive::train: - sturdy 4kb frontend framework
Fast.js
Faster user-land reimplementations for several common builtin native JavaScript functions.