Add a timeout to any promise

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A promise has no built-in time limit, so a stalled request can hang a program forever. The deadline function wraps any promise and rejects it after a given number of milliseconds. The abortable function does the same with an AbortSignal, which lets a user or another event cancel the wait.

import { abortable, deadline, delay } from "jsr:@std/async";

When the promise settles before the time limit, deadline resolves with its value as if the wrapper was not there.

const fast = delay(50).then(() => "fetched 3 records");
console.log(await deadline(fast, 1_000)); // fetched 3 records

When the time limit hits first, deadline rejects with a DOMException named TimeoutError.

const slow = delay(2_000, { persistent: false }).then(() => "too late");
try {
  await deadline(slow, 100);
} catch (err) {
  console.log((err as DOMException).name); // TimeoutError
}

The rejection only stops the waiting. The slow task above keeps running in the background unless it accepts a signal and honors it, so pass an AbortSignal to the underlying work whenever you can.

The abortable function ties a promise to an AbortSignal instead of a clock. Here the same signal also cancels the underlying delay, so no work is left running after the abort.

const controller = new AbortController();
const work = delay(2_000, { signal: controller.signal })
  .then(() => "report ready");

setTimeout(() => controller.abort(), 50);

try {
  await abortable(work, controller.signal);
} catch (err) {
  console.log((err as DOMException).name); // AbortError
}

Run this example locally using the Deno CLI:

deno run https://docs.deno.com/examples/scripts/promise_timeout.ts

Add a timeout to any promise

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