This is a list of open source projects I personally used to learn different aspects of Javascript development (backend and frontend).
It is very, very incomplete. I am trying to figure out an efficient way to discover and classify projects that others can learn by contributing. If you have any ideas, please help me!
Feel free to add your favorite project and what other can learn from it!
/~https://github.com/babel/babel/tree/master/packages/babel-parser - learn how works javascript parser that powers popular tools like babeljs and prettier
/~https://github.com/kentcdodds/babel-plugin-macros - learn how to write a babeljs plugin
/~https://github.com/webpack/tapable - learn a generic hooks-based architecture that powers webpack
/~https://github.com/ncthbrt/nact - learn about nano-services from this NodeJS implementation
/~https://github.com/GoogleChromeLabs/prerender-loader/blob/master/src/index.js - ???
/~https://github.com/tcoopman/image-webpack-loader -learn how to write a simple webpack plugin
/~https://github.com/willyelm/pug-html-loader - learn how to write a simple webpack loader
/~https://github.com/aholachek/animate-css-grid - learn how to animate complex layouts
/~https://github.com/nosir/cleave.js - learn how to format input text + how to create a library that works both for react and for angular
/~https://github.com/streamich/react-use - an excellent collection of ReactJS hooks
/~https://github.com/jaredpalmer/formik - to learn all the aspect of effecient forms validation
/~https://github.com/mui-org/material-ui - you will learn how to create a large-scale, themable, high-quality components library
/~https://github.com/Semantic-Org/Semantic-UI - another example of large-scale and themable compontents library
/~https://github.com/jamiebuilds/unstated - you will learn how to create simple and effective state management frameworks for ReactJS applications
/~https://github.com/GantMan/ReactStateMuseum - a compilation of different examples to managing state for ReactJS applications