WTF, JavaScript?!
Prove you actually know it.
268 challenges that will make you question everything you think you know about this language. 99 hands-on coding problems judged by a merciless sandbox — the rest are brutal multiple choice and drag-and-drop mind games. Every challenge ships a hint. Using it is between you and your ego.
casuals welcome — egos enter at their own risk
Topics
Play in your terminal
npm install -g wtfjavascript # or: bun add -g wtfjavascript wtfjs # full styled quiz in your terminal wtfjs --topic "Proxy & Reflect" npx wtfjavascript # or: bunx wtfjavascript (zero-install)
Read the books behind the pain
The book series that goes deeper than any challenge here can. Scope, closures, this, coercion — explained properly, from the spec up. The entire series is free to read on GitHub, with print editions available from the same page.
Acknowledgments
Every challenge here stands on work that others gave away for free. Lydia and Kyle spent years writing the questions and books that teach this language to anyone willing to learn — hours of unpaid, careful work done purely to help the community. If these challenges taught you something, it's because they taught us first. Thank you. Go star their work.
