Free Software for JavaScript
Hapi
Build powerful, scalable applications, with minimal overhead and full out-of-the-box functionality with Hapi. It's a free and open-source JavaScript framework for Node.js that is developed for enterprise-grade applications. Companies like Walmart, Brave and Condé Nast build web-services with Hapi and rely on it at scale.
Webpack
Webpack is an open-source module bundler for JavaScript. Its main purpose is to bundle JavaScript files for usage in a browser, yet it is also capable of transforming, bundling, or packaging just about any resource or asset. It can transform front-end assets like HTML, CSS, and images where corresponding loaders ar included and takes modules with dependencies and generates static assets representing those modules.
AlaSQL
AlaSQL is a free and open-source lightweight client-side in-memory SQL database designed to work in browser and Node.js. The database is written in JavaScript and does not use the browsers WebSQL database. The AlaSQL server is fully functional and supports JOINs, GROUPs, UNIONs, ANY, ALL, IN, subqueries and very limited transactions support.
Rome
Rome is a free and open-source JavaScript build tool that has strong conventions and aims to have minimal configuration. The toolset includes a linter, compiler and bundler for JavaScript, TypeScript, JSON, HTML, Markdown, and CSS. Rome has zero dependencies, and has largely been written from scratch by people from Facebook.
Gulp.js
A toolkit to automate & enhance your workflow. Leverage gulp and the flexibility of JavaScript to automate slow, repetitive workflows and compose them into efficient build pipelines.
Grunt.js
Grunt is an open-source JavaScript task runner, a tool used to automatically perform frequent tasks such as minification, compilation, unit testing, and linting. The Grunt ecosystem contains hundred of plugins that can be used to automate just about anything build related. With Grunt, you use the command-line interface to run custom tasks defined in a your config file to optimize your development workflow.
Vizzu
Vizzu is a free, open-source Javascript/C++ library utilizing a generic dataviz engine that generates many types of charts and seamlessly animates between them. It can be used to create static charts but more importantly it is designed for building animated data stories and interactive explorers as Vizzu enables showing different perspectives of the data that the viewers can easily follow due to the animation.
SvelteKit
SvelteKit is a free and open-source framework used to create SSR, Static and Serverless web applications with Svelte. SvelteKit aims to replace Sapper and in the process unify the eco-system and have a single way to start building apps with Svelte. This will simplify on-boarding, and reduce maintenance and support burden for the core developers. SvelteKit fully embraces the serverless paradigm and has support for all the major serverless providers. Under the hood, SvelteKit uses Snowpack in development and compiles and hot reloads your code near instantly, making it an extremely pleasant developer experience.
D3.js
With D3.js developers can produce dynamic, interactive data visualizations in web browsers. It's a free and opne-source JavaScript library that combines Scalable Vector Graphics, HTML5, and Cascading Style Sheets standards. The library gives developers the full capability of modern browsers and puts a strong emphasis on web standards.