Timers

Node has the browser’s setTimeout and setInterval, plus its own setImmediate. And a much nicer promise-based API.

The Classics

setTimeout(() => console.log("once, later"), 1000);

const id = setInterval(() => console.log("forever"), 1000);
// later:
clearInterval(id);

Browser-identical. Returns a Timer object (not a number, but it works the same).

setImmediate

Run as soon as the current phase finishes, before any other timer:

setImmediate(() => console.log("next loop iteration"));
setTimeout(() => console.log("after 0ms"), 0);
// 'next loop iteration' typically prints first

setImmediate(fn) is preferable to setTimeout(fn, 0) in Node — it’s defined to run at a specific phase, not “approximately zero ms from now.”

Promise-Based Timers

node:timers/promises lets you await instead of callback:

import { setTimeout as wait } from "node:timers/promises";

await wait(500);
console.log("half second later");

Much cleaner inside async functions.

Unrefing

A pending setTimeout keeps the process alive. To say “this timer shouldn’t hold the process open”:

const id = setTimeout(() => doThing(), 60_000);
id.unref();   // process can exit before this fires

Useful for periodic cleanup tasks that shouldn’t prevent shutdown.

A Scheduling Pattern

import { setTimeout as wait } from "node:timers/promises";

async function pollForever() {
  while (true) {
    await checkSomething();
    await wait(5_000);
  }
}

setInterval can drift if a tick is slow. The await wait(...) pattern guarantees fixed gaps between work.