onDocumentFocus

onDocumentFocus(fn) registers a callback that runs with the current document focus state — true when the document has focus, false when it loses it. It fires immediately with the initial state and then on every window focus / blur. For a reactive accessor instead of a callback use useDocumentFocus. Part of pota/use/focus.

The subscription is scoped to the surrounding reactive owner, so call it inside a component or another reactive scope; it cleans up automatically when that scope is disposed.

Arguments

Argument	Type	Description
fn	(focused: boolean) => …	Called with the current focus state now and on every change.

Examples

Subscribe to focus changes

Logs whenever the browser tab/window gains or loses focus, starting with its current state.

import { render, signal } from 'pota'
import { onDocumentFocus } from 'pota/use/focus'

function App() {
	const log = signal('switch tabs to see focus events')

	onDocumentFocus(focused =>
		log.write(focused ? 'gained focus' : 'lost focus'),
	)

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

render(App)