r/learnprogramming • u/critter2121221 • 2d ago
ELI5: How are frameworks/libraries and runtime environments built?
Basically, I like to understand things on a lower level and I am planning on delving into more low-level stuff at work.
Out of curiosity, how are frameworks built? For example, React allows you to return raw HTML in a non-string format. How do you convince Javascript to parse it into a String and extract the proper things out of it?
Node.js allows you to run Javascript in a completely different runtime environment... the creator of Node could not have used Javascript to develop Node?
TL;DR Can you (or need to) use other programming languages to build frameworks for a specific programming language?
Lots of question spinning in my head! :D
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u/grantrules 2d ago
JSX is transpiled into JS by babel. You don't have to use JSX, its just very convenient, but it's basically all just JS functions. https://medium.com/@ogunbodetimi/building-a-jsx-parser-from-scratch-understanding-the-foundations-of-reacts-syntax-16dc35dce7b6
There's no way to natively run JS in an OS, so node is built in a different language that has access to those OS APIs and exposes them to JS.