JSS is an authoring tool for CSS which uses JavaScript as a host language.
Jxnblk's Palx
Automatic UI Color Palette Generator.
Kaboom
JavaScript game programming library that helps you make games fast and fun.
Knockout
Knockout makes it easier to create rich, responsive UIs with JavaScript.
Koa
Expressive middleware for node.js using ES2017 async functions
Kroki
Creates diagrams from textual descriptions!
L3MON
L3MON - Remote Android Managment Suite.
LangGraph
I may be late to the party, but LangGraph lets you build complex workflow architectures and codify them as powerful automations. Also LLMs, if you want. But you don’t have to!
lax.js
Simple & lightweight (<4kb gzipped) vanilla JavaScript library to create smooth & beautiful animations when you scroll.
Lazy.js
Lazy.js is a functional utility library for JavaScript, similar to Underscore and Lodash, but with a lazy engine under the hood that strives to do as little work as possible while being as flexible as possible.
Leaflet
🍃 JavaScript library for mobile-friendly interactive maps