Free Software for JavaScript
JerryScript
JerryScript is a lightweight JavaScript engine for resource-constrained devices such as microcontrollers. It can run on devices with less than 64 KB of RAM and less than 200 KB of flash memory.
Underscore.js
Underscore.js is a free and open-source JavaScript library that provides over 100 functional programming helpers without extending any built-in objects. Underscore.js can be used for function binding, javascript templating, creating quick indexes, deep equality testing, and much more.
Socket.io
Socket.IO is a free and open-source JavaScript library that can be used for building realtime web applications. The library consists of two parts, a server-side library for Node.js and a client-side library that runs in the browser.
dORM
dORM is a lightweight SQL query builder for Deno and PostgreSQL and is currently being expanded into a full-fledged object-relational mapping (ORM) tool. Its purpose is to make your life easier when making SQL queries and let you write queries in familiar Javascript/Typescript syntax and dot notation.
Webiny
Webiny is a free and open-source static site generator and headless CMS written in JavaScript.
RequireJS
RequireJS is a free and open-source JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, like Node.js and Rhino.
Pug.js
Pug or Pug.js is a free and open-source, high-performance template engine for Node.js. The library is heavily influenced by Haml and share many of the same concepts, while being a JavaScript implementation.
Vest
Vest is a free and open-source validations library for JavaScript applications. The library share many similarities with other testing framework such as Mocha and Jest. It is to write validation testing with Vest as it includes already common declarative patterns. The library can handle validation upon user interaction and user input.
Guess.js
Guess.js is a free and open-source library that provides tools to simplify predictive data-analytics driven approaches to improving user-experiences on the web. The library is written in JavaScript and aims to lower the friction of consuming and applying this thinking to all modern sites and apps, including building libraries & tools for popular workflows.