How to cancel a fetch request?
Assesses fundamental understanding of JavaScript conventions, runtime behavior, and memory/performance considerations.
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Until a few days back, One shortcoming of native promises is no direct way to cancel a fetch request. But the new AbortController from js specification allows you to use a signal to abort one or multiple fetch calls.
The basic flow of cancelling a fetch request would be as below,
- Create an
AbortControllerinstance - Get the signal property of an instance and pass the signal as a fetch option for signal
- Call the AbortController's abort property to cancel all fetches that use that signal
For example, passing the same signal to multiple fetch calls will cancel all requests with that signal,
const controller = new AbortController();
const { signal } = controller;
fetch("http://localhost:8000", { signal })
.then((response) => {
console.log(`Request 1 is complete!`);
})
.catch((e) => {
if (e.name === "AbortError") {
// We know it's been canceled!
}
});
fetch("http://localhost:8000", { signal })
.then((response) => {
console.log(`Request 2 is complete!`);
})
.catch((e) => {
if (e.name === "AbortError") {
// We know it's been canceled!
}
});
// Wait 2 seconds to abort both requests
setTimeout(() => controller.abort(), 2000);
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.