postrouter

React router with componentless route matching

Features

• componentless route matching
  • doesn't enforce route collocation and tight coupling within a route hierarchy;
  • works the same way both for components and dynamic route-based prop values;
  • is akin to the common React pattern of conditional rendering;
• the history-based route link component <A> with the props similar to those of the ordinary HTML link <a> (allowing for quick migration back and forth and working more like a polyfill to the ordinary link);
• the <Router> component fit for both browser and server rendering;
• the utility converting plain HTML links (that can't be easily replaced with React components) to history-based links.

Example

import {createRoot} from 'react-dom/client';
import {useRoute, A} from 'postrouter';

const AppRoute = {
    HOME: '/',
    INTRO: '/intro',
    SECTION: /^\/section\/(?<id>\d+)\/?$/,
};
const allKnownRoutes = Object.values(AppRoute);

const App = () => {
    // the `useRoute()` hook subscribes the component to URL changes
    const [route, withRoute] = useRoute();

    return (
        <div className="app">
            <nav>
                {/* the route link component `A` looks similar to the
                    plain HTML link as it serves a similar purpose */}
                <A href={AppRoute.HOME}
                    // `withRoute()` checks the current location and
                    // works similar to the conditional ternary operator;
                    // below, it roughly means:
                    // `home location ? 'active' : undefined`
                    // (the omitted third argument is `undefined`)
                    className={withRoute(AppRoute.HOME, 'active')}>
                    Home
                </A>
                {' | '}
                <A href={AppRoute.INTRO}
                    className={withRoute(AppRoute.INTRO, 'active')}>
                    Intro
                </A>
            </nav>
            {withRoute(AppRoute.HOME, (
                <main id="home">
                    <h1>Home</h1>
                    <ul>
                        <li>
                            <A href="/section/1">Section #1</A>
                        </li>
                        <li>
                            <A href="/section/2">Section #2</A>
                        </li>
                    </ul>
                </main>
            ))}
            {/* although `withRoute()` calls may appear in groups like
                in this example, they work independently from each other
                and may as well be used uncoupled in different places of
                an application */}
            {withRoute(AppRoute.INTRO, (
                <main className="section" id="intro">
                    <h1>Intro</h1>
                </main>
            ))}
            {/* the second and the third argument of `withRoute()` can
                be functions of `{href, params}`, with `params`
                containing the capturing groups of the location pattern
                if it is a regular expression */}
            {withRoute(AppRoute.SECTION, ({params}) => (
                <main className="section">
                    <h1>Section #{params.id}</h1>
                </main>
            ))}
            {/* below, rendering `null` if the current location
                matches `allKnownRoutes`, and the 404 error screen
                otherwise */}
            {withRoute(allKnownRoutes, null, (
                <main className="error section">
                    <h1>404 Not found</h1>
                </main>
            ))}
            <footer>
                <hr/>
                <button onClick={() => {
                    // `route` has a `window.location`-like API and can
                    // be handy for direct manipulation of the location
                    route.assign(AppRoute.HOME);
                }}>
                    Home
                </button>
            </footer>
        </div>
    );
};

createRoot(document.querySelector('#app')).render(<App/>);

The route object returned from the useRoute() hook is an instance of the Location class provided by the wrapping <Router> component. If there is no <Router> up the React node tree (like with <App/> in the example above), a default route based on the current page location is used. A wrapping <Router> can be useful to provide a custom route prop value that accepts either a string location or a Location class instance.

Custom routing

The default route object returned from the useRoute() hook responds to changes in the entire URL, with pathname, search, and hash combined. This can be changed by providing an instance of a customized extension of the Location class to the Router component.

import {createRoot} from 'react-dom/client';
import {Router, Location, getPath} from 'postrouter';

export class PathLocation extends Location {
    deriveHref(location) {
        // disregarding `search` and `hash`
        return getPath(location, {search: false, hash: false});
    }
}

createRoot(document.querySelector('#app')).render(
    <Router route={new PathLocation()}>
        <App/>
    </Router>
);

Extending the Location class gives plenty of room for customization. This approach allows in fact to go beyond the URL-based routing altogether.

Server-side rendering (SSR)

For the initial render on the server, the <Router> component can be used to pass the current route location to the application in essentially the same way as it can be done in the client-side code:

// On the Express server
app.get('/', (req, res) => {
    const html = ReactDOMServer.renderToString(
        <Router route={req.originalUrl}><App/></Router>
    );

    // Sending the resulting HTML to the client.
});

Converting plain links

The useRouteLinks() hook can be helpful when it's necessary to convert plain HTML links to SPA route links if the route link component is not applicable right away (for instance, in a server-fetched static chunk of HTML content):

useRouteLinks(containerRef, '.content a');
// `containerRef` is a value returned from the React's `useRef()` hook.