Children as a function 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 Toggle({ initial = false, children }) whose children is a function receiving { on, toggle, setOn } and returning what to render; Toggle owns the state. Then use it in Details({ summary, children }): a <button className="summary"> showing the summary that toggles, and <div className="content"> with the children shown only while open.
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.