CS50's Mobile App Development with React Native

Before you spend a weekend on this, read the notice at the top of the course page: CS50M was retired on 30 June 2020 and is officially deprecated. The material stays online for archive purposes. Harvard is not maintaining it, nobody is answering questions on it, and the React Native it teaches is five-plus years behind the framework you'd install today.

That said, it was a genuinely excellent course. Jordan Hayashi taught it with David Malan's CS50 production behind him, and Hayashi's lectures are still some of the clearest explanations of JavaScript closures, the event loop and React's rendering model that exist on video. The problem isn't the teaching. It's the shelf life.

What the thirteen weeks covered

JavaScript and the ES6/ES7 additions, React and JSX, component architecture, then React Native proper: user input, debugging, navigation, data, Redux for state, performance, testing and deployment. Students finished with a self-designed app of their own.

Note how much of that list is not React Native. Roughly the first third is a JavaScript and React course, and that third has aged far better than the rest.

What five years does to a mobile course

Quite a lot. Navigation libraries have gone through breaking major versions. Redux is no longer the default answer to state and the community's centre of gravity moved to hooks, context, and query libraries. Expo's workflow is unrecognisable. The New Architecture — Fabric and TurboModules — did not exist in this material at all. Follow the setup steps literally and you will not get a running project.

The lecture videos on JavaScript fundamentals, though, don't rot. Closures work the way Hayashi says they do.

Who it's for — and who should skip it

Worth mining if you want strong conceptual lectures on JavaScript and React from a very good teacher, and you're happy to treat the React Native half as historical. Also worth it if you like the CS50 problem-set format and want the exercises for practice.

Skip it if you want to build a shippable app. Genuinely — skip it. Following a deprecated mobile course end to end is a specific kind of frustrating, because you'll spend your debugging time on dependency resolution rather than on anything you're trying to learn. Start with Expo's current tutorial instead.

Our take

A great course that the directory should probably be labelling as an archive rather than a recommendation. Take the JavaScript and React lectures, leave the rest, and don't expect anything to install cleanly. The Harvard name on it is doing more work than the content currently justifies.