watch with cleanup in Vue
Vue interview exercise on Computed & watchers, difficulty 3 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 Search with a prop `lookup` ((term: string) => Promise<string[]>): an <input> bound to a query ref, a <ul> of <li> results and <p class="none">No matches</p> when a non-empty query has none. Watch the query: a blank query clears the results without calling lookup; otherwise call lookup with the trimmed query and show what it returns. Answers that arrive after the query has changed again must be ignored (use the watcher's onCleanup).
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.