The JavaScript setTimeout() method

Q: How do I delay code in JavaScript?

Use setTimeout(callback, delay) with the delay in milliseconds, e.g. setTimeout(fn, 2000) for two seconds.

Q: How do I cancel a setTimeout()?

Keep the id it returns and call clearTimeout(id) before the delay elapses.

Q: What is the difference between setTimeout() and setInterval()?

setTimeout() runs once after a delay; setInterval() runs repeatedly every interval until cleared.

Method JavaScript All modern browsers Updated June 23, 2026

Quick answer

The setTimeout() method runs a function once after a delay given in milliseconds. setTimeout(() => alert("Hi"), 2000) waits two seconds, then runs. It returns a timer id you can pass to clearTimeout() to cancel. The delay is a minimum, not a guarantee — the callback runs after the current code finishes.

Overview

setTimeout() schedules a function to run once, later. You pass the function and a delay in milliseconds (so 1000 is one second), and after that time the function is queued to run. It's how you defer work — show a message after a pause, retry after a delay, debounce rapid input.

It returns a numeric timer id, and that id is your cancel handle: const t = setTimeout(fn, 5000); clearTimeout(t); stops it before it fires. Any arguments after the delay are passed along to your callback when it runs.

Two things commonly surprise people. First, the delay is a minimum, not exact: JavaScript is single-threaded, so the callback waits until the current code and earlier tasks finish — a busy thread can push it later than you asked. Second, setTimeout(fn, 0) doesn't run immediately; it defers fn until after the current script, a useful trick for letting the browser update first. For something that repeats on an interval, use setInterval() instead.

Syntax

const id = setTimeout(callback, delay)
const id = setTimeout(callback, delay, arg1, arg2)

const id = setTimeout(() => console.log("later"), 1000);
clearTimeout(id);  // cancel it

Parameters

The setTimeout() method accepts the following parameters.

Parameter	Description
`callback`	The function to run after the delay.
`delay`	Time to wait in milliseconds before running (a minimum, not exact). Defaults to `0`.
`arg1 ... argN`	Optional. Extra arguments passed to the callback when it runs.

Example

Live example

<p id="out" style="font:15px system-ui">Waiting 2 seconds...</p>
<script>
  setTimeout(() => {
    document.getElementById('out').textContent = 'Done! Two seconds passed.';
    document.getElementById('out').style.color = '#16a34a';
  }, 2000);
</script>

Best practices

Remember the delay is in milliseconds and is a minimum — not a precise guarantee.
Keep the returned id and call clearTimeout(id) to cancel a pending timeout.
Use setTimeout(fn, 0) to defer work until after the current code runs.
For repeating work, use setInterval() rather than re-scheduling manually (unless you need precise spacing).

Frequently asked questions

How do I delay code in JavaScript?

Use setTimeout(callback, delay) with the delay in milliseconds, e.g. setTimeout(fn, 2000) for two seconds.

How do I cancel a setTimeout()?

Keep the id it returns and call clearTimeout(id) before the delay elapses.

Is the setTimeout() delay exact?

No — it's a minimum. The single-threaded event loop runs the callback only after the current code and earlier tasks finish, so it can be later than requested.

What is the difference between setTimeout() and setInterval()?

setTimeout() runs once after a delay; setInterval() runs repeatedly every interval until cleared.

setInterval() showModal()

References