untrack

Runs fn without establishing reactive dependencies on anything it reads. Use it inside a tracking scope when you want a value's current snapshot but don't want to re-run when it later changes. For the explicit-deps form of an effect, see on. signal's update(prev => next) wraps the read in untrack internally.

Arguments

name	type	description
fn	() => T	function whose reads should not subscribe

Returns: the return value of fn.

Examples

Snapshot a signal in an effect

Inside a tracking scope (effect, memo, derived), reading a signal subscribes the surrounding scope to its changes. Wrap the read in untrack(() => …) when you want the value at this moment but don't want to re-run when it later changes.

import { effect, render, signal, untrack } from 'pota'

function App() {
	const a = signal(1)
	const b = signal(10)
	const log = signal('')

	effect(() => {
		// Re-runs only when `a` changes; `b` is read snapshot-style.
		log.write(`a = ${a.read()}, b was ${untrack(() => b.read())}`)
	})

	return (
		<div>
			<p>{log.read}</p>
			<button on:click={() => a.update(n => n + 1)}>a++</button>
			<button on:click={() => b.update(n => n + 1)}>b++</button>
		</div>
	)
}

render(App)