Node.js simplifies development by letting you use a single language on the client and server. This has the added benefit of keeping your apps DRY because you can share code between them.
Its package registry, npm, is the largest of any language. With over 500,000 packages and 500+ new packages being registered every day, you can almost always find what you're looking for. And if you can't, why not make your own and share it with the world?
PostCSS essentially allows you to set up your own CSS preprocessor with the features that matter to you. It has a modular plugin-based architecture, which means that if someone comes up with a useful new feature, you can easily add it to your stack as a PostCSS plugin. PreCSS and PostCSS-cssnext are some of my go-to plugins.
Discord is home to many game development communities, including AGDG (Amateur Game Development General), RGD (Reddit Game Development), and Game Dev League. When I'm working with WebGL, they are always very knowledgeable and helpful in answering my questions about physics, vectors and data structures.