wp-calypso/client/lib/detect-history-navigation/README.md

detect-history-navigation

This module determines when a page has been rendered via the history event (back or forward buttons, or via the history methods) versus being a newly navigated page (e.g., via clicking a link to a page).

This can be used alongside the Calypso Router module by calling the start() method of this module prior to the start() method of page.js.

import page from '@automattic/calypso-router';
import detectHistoryNavigation from 'detect-history-navigation';

detectHistoryNavigation.start();
page.start();

Then controllers and components can call detectHistoryNavigation.loadedViaHistory() which returns a boolean determining whether the current route is being loaded from a history event or is a fresh pageload.

Components that are mounted into the initial view of a page that is loaded by history can detect this in componentWillMount, componentDidMount, and the initial run of their render method. After the initial render loadedViaHistory() will return false.