Effects & refs in React: interview exercises

Effects & refs in React: 5 test-checked interview exercises (Syncing with the outside: useEffect), each beside a worked example, with tests as you go. Free.

1. Syncing with the outside: useEffect
2. Subscribe, then unsubscribe
3. An interval with cleanup
4. Refs: a DOM handle and a value that does not render
5. Loading data, ignoring stale answers

Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Progress is saved in your browser, and in your account if you sign in.

More React topics

• Components & JSX
• State
• Custom hooks
• Context & reducers
• Performance
• React 19
• Patterns

All React exercises · Other languages and frameworks