onMutations

onMutations(node, fn, init?) calls fn with each batch of MutationRecords observed on node — the callback half of the pota/use/mutation emitter pair. For a reactive accessor use useMutations; to attach an observer declaratively use mutated. The default init is { childList: true, subtree: true }.

fn is only ever called with a real MutationRecord[] batch — the pre-observer placeholder is filtered out.

Arguments

Argument	Type	Description
node	Node	Element to observe.
fn	(records: MutationRecord[]) => void	Called with each batch of records.
init	MutationObserverInit	Optional observer config; defaults to childList + subtree.

Examples

Subscribe to mutations

Register a callback that logs each MutationRecord[] batch observed on a node you already hold a reference to.

import { render, signal } from 'pota'
import { onMutations } from 'pota/use/mutation'

function App() {
	const log = signal('mutations will appear here')

	onMutations(document.body, records => {
		log.write(`mutations: ${records.length}`)
	})

	return <p>{log.read}</p>
}

render(App)