Most async code in frontend apps has a hidden bug: it doesn't stop when it should. A user navigates away mid-request. A component unmounts. A newer search query supersedes the previous one. The old network call keeps running, eventually resolves, and tries to update state that no longer exists. In React, that's the infamous warning: "Can't perform a React state update on an unmounted component." In vanilla JS, it silently delivers stale data.
AbortController is the browser's built-in solution. It's been in every major browser since 2018 — old enough that there's no excuse not to use it. But most tutorials skip it, most codebases use it inconsistently, and most devs reach for it only after they've debugged a flicker one too many times.
Here's the pattern, end to end.
The race condition you already have
function SearchResults({ query }: { query: string }) {
