About const foo

Most learning resources are written for people starting out. Once you've shipped software for five or ten years, the tutorials stop being written for you — but the learning doesn't stop mattering. The gap between a good engineer and a great one is understanding how things actually work.

const foo is built for that gap: how engines optimize your code, how production backends fail, how attackers read your endpoints, what the borrow checker is really telling you, and what you can learn from reading the source of the tools you use every day.

Every lesson mixes prose with exercises you can solve without typing — reorder the lines, spot the broken variant, predict the output and watch the snippet actually run in your browser. Deep enough to be worth your time, light enough to do on your phone.

Progress is saved locally in your browser. No account, no tracking, no paywall.