An error boundary in React
React interview exercise on Patterns, difficulty 2 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Write ErrorBoundary({ fallback, children }) where fallback is a function (error, reset) => ReactNode: render the children; when one of them throws during render, render fallback with the error and a reset function that renders the children again. Healthy children render untouched.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.