How to detect route changes with react-router v4?

Question

I need to detect if a route change has occurred so that I can change a variable to true.

I've looked through these questions:
1. https://github.com/ReactTraining/react-router/issues/3554
2. How to listen to route changes in react router v4?
3. Detect Route Change with react-router

None of them have worked for me. Is there a clear way to call a function when a route change occurs.

Answer 1

One way is to use the withRouter higher-order component.

Live demo (click the hyperlinks to change routes and view the results in the displayed console)

You can get access to the history object's properties and the closest 's match via the withRouter higher-order component. withRouter will pass updated match, location, and history props to the wrapped component whenever it renders.

https://github.com/ReactTraining/react-router/blob/master/packages/react-router/docs/api/withRouter.md

import {withRouter} from 'react-router-dom';

class App extends Component {
    componentDidUpdate(prevProps) {
        if (this.props.location.pathname !== prevProps.location.pathname) {
            console.log('Route change!');
        }
    }
    render() {
        return (
            <div className="App">
                ...routes
            </div>
        );
    }
}

export default withRouter(props => <App {...props}/>);

---

Another example that uses url params:

If you were changing profile routes from /profile/20 to /profile/32

And your route was defined as /profile/:userId

componentDidUpdate(prevProps) {
    if (this.props.match.params.userId !== prevProps.match.params.userId) {
        console.log('Route change!');
    }
}

Answer 2

With React Hooks, it should be as simple as:

useEffect(() => {
    const { pathname } = location;
    console.log('New path:', pathname);
}, [location.pathname]);

By passing location.pathname in the second array argument, means you are saying to useEffect to only re-run if location.pathname changes.

Live example with code source: https://codesandbox.io/s/detect-route-path-changes-with-react-hooks-dt16i