The Hitchhiker‘s Guide to React Router v4: the hidden value of route config

React applications can be complex beasts. As the user navigates through the app, different data needs to be loaded from APIs, different components need to appear or disappear, and the URL needs to change to reflect the new state. This dance between components, data, and routes can quickly get unwieldy.

Enter React Router—the popular routing library for keeping your UI in sync with the URL. While React Router is indeed widely used, many developers fail to tap into its full potential. Sure, you can get by with peppering your code with hardcoded <Route> components, but as your app grows, this approach can lead to mounting complexity and missed optimization opportunities.

The solution lies in the unassuming routes prop—an optional feature that enables you to centralize all your route config into a single data structure. In this guide, we‘ll dive deep into the what, why, and how of the routing config pattern. By the end, you‘ll have a powerful new tool in your React architecture toolbox. Let‘s jump in!

A brief history of React routing

To understand the benefits of route configs, it‘s helpful to look at how React routing has evolved over the years. The initial versions of React Router used a fairly imperative API. You‘d define your routes something like this:

const routes = (
  <Router>
    <Route path="/" component={Home} />
    <Route path="/about" component={About} />
    <Route path="/contact" component={Contact} />
  </Router>
);

Not terrible, but as your app grew in complexity, a few pain points emerged:

1. JSX spaghetti: Complex routing logic led to bloated, hard-to-read JSX. The hierarchy and structure of routes was difficult to discern at a glance.

2. Scattered definitions: Related routes were often defined in separate components, making it tough to get a bird‘s-eye view of the app‘s routing structure.

3. Lack of reusability: There was no easy way to share common routing patterns between different parts of the app.

React Router v4 introduced a component-based API that alleviated some of these issues. Instead of JSX route definitions, you could define your routes with plain component composition:

const App = () => (
  <Router>
    <div>
      <Route exact path="/" component={Home} />
      <Route path="/about" component={About} />
      <Route path="/contact" component={Contact} />
    </div>
  </Router>
);

This was a step in the right direction. However, the issue of scattered route definitions remained—as the app grew, routes would often sprawl across many different components.

This is where the route config comes in. By centralizing your routes into a single JavaScript object, you can get the best of both worlds: a clear, concise representation of your app‘s structure combined with the composability of the component-based approach.

The power of the route config

Let‘s take a closer look at some of the key benefits of using a centralized route config.

Separation of concerns

One of the biggest advantages is the clean separation between routing logic and UI components. With hardcoded <Route> components, it‘s easy for these concerns to get tangled up. Components that should be focused on rendering UI and handling user interactions now also need to be aware of the app‘s routing structure.

In contrast, a route config keeps these concerns neatly separated. The config is solely responsible for defining the mapping between URLs and components, while the components themselves can remain blissfully unaware of the routes they‘re involved in.

This separation makes the code more maintainable in the long run. Changes to the routing structure can be made in a single place without touching multiple components.

High-level view of app structure

Another huge benefit is the bird‘s-eye view of your app‘s structure that a route config provides. It acts as a pseudo site-map, giving developers (and project stakeholders) a quick way to grasp the high-level structure of the application.

With hardcoded routes, it‘s difficult to "see the forest for the trees". You have to mentally piece together the various <Route> elements scattered across different components to build up an overall picture of the app‘s routing. In contrast, a route config array collects all the key structural information—URLs, components, and route nesting—into a single, readable data structure.

This high-level perspective is especially valuable for large, complex applications. New developers can quickly get a sense of the key pages and flows just by skimming the route config. Project managers and less technical stakeholders can also more easily review and give feedback on the app‘s structure without getting lost in the implementation details.

Enabling advanced patterns

Beyond the maintainability and readability benefits, the route config pattern also enables some powerful advanced routing techniques.

One example is route-based code splitting. This performance optimization involves splitting your JavaScript bundle into multiple chunks based on the routes. Only the code needed for the initial route is loaded, and additional chunks are loaded on-demand as the user navigates to different parts of the app.

Implementing code splitting with a route config is straightforward. Instead of referencing a component directly, you specify a function that dynamically imports the component:

const routes = [
  {
    path: ‘/‘,
    component: () => import(‘./components/Home‘),
  },
  {
    path: ‘/blog‘,
    component: () => import(‘./components/Blog‘),
  },
];

During the build process, tools like webpack will see these dynamic imports and split the code into separate chunks automatically. When a user navigates to a new route, React Router will call the corresponding import function to lazy load the required component. All of this complexity is handled elegantly by the router, and the developer simply defines the splitting strategy in the route config.

Another advanced use case is server-side rendering. For large applications, rendering the initial HTML on the server can lead to significant performance benefits. However, managing server-rendered routes with hardcoded <Route> components can be tricky.

With a route config, server-side rendering becomes much more manageable. The config acts as a single source of truth that can be shared between the client and server. The server can iterate through the config to determine which components to render for a given URL, without having to replicate the client-side routing logic.

Encouraging a componentization mindset

One of the more subtle benefits of the route config pattern is how it encourages a componentization mindset.

With hardcoded <Route> elements, it‘s easy to fall into the trap of creating "god components"—huge components that handle a wide variety of responsibilities and end up being a nightmare to maintain. When routes are defined as an afterthought within individual components, those components naturally tend to become more bloated.

In contrast, centralizing your routes pushes you to think more carefully about the componentization of your UI. You‘re encouraged to break your interface down into smaller, single-responsibility components that can be composed together via the route config.

This mindset shift can lead to a more modular, reusable component architecture. Instead of thinking about your UI as a set of pages with hardcoded routes, you start thinking in terms of reusable components that can be mixed and matched via the route config. This can lead to a more flexible, maintainable application over the long run.

Implementing a route config

Sold on the benefits of a centralized route config? Let‘s walk through a concrete example of how to implement this pattern in a React application.

First, we‘ll define our config array:

const routes = [
  {
    path: ‘/‘,
    component: Home,
    exact: true,
  },
  {
    path: ‘/about‘,
    component: About,
  },
  {
    path: ‘/blog‘,
    component: Blog,
    routes: [
      {
        path: ‘/blog/:postId‘,
        component: Post,
      },
    ],
  },
];

Each object in the routes array represents a route, with a path and a component to render when that path is matched. The exact flag indicates that the path should only match if it exactly matches the URL (useful for the root route). Nested sub-routes are specified with a routes array on the parent route object.

Next, we‘ll replace our hardcoded <Route> elements with a loop that maps over the routes array:

const App = () => (
  <Router>
    <div>
      {routes.map((route, i) => (
        <RouteWithSubRoutes key={i} {...route} />
      ))}
    </div>
  </Router>
);

The key piece here is the <RouteWithSubRoutes> component. This is a custom wrapper that renders a <Route> with the given component, as well as any sub-routes:

const RouteWithSubRoutes = (route) => (
  <Route 
    path={route.path}
    exact={route.exact}
    render={(props) => (
      <route.component {...props} routes={route.routes} />
    )}
  />
);

If the route has a routes array, the RouteWithSubRoutes component will pass those sub-routes down to the rendered component as a prop. The component can then render those sub-routes as needed:

const Blog = ({ routes }) => (
  <div>

    <Route exact path="/blog" component={PostList} />
    {routes.map((route, i) => (
      <RouteWithSubRoutes key={i} {...route} />
    ))}
  </div>
);

And that‘s the core implementation! By recursively mapping over the route config and rendering RouteWithSubRoutes, we can handle route hierarchies of arbitrary depth.

Best practices for route configs

As you start using route configs in your own applications, there are a few best practices to keep in mind:

Keep configs minimal

The route config‘s job is to define the mapping between URLs and components, not to handle the actual rendering logic. Keep your config objects as minimal as possible, and move any complex logic into the components themselves.

A good rule of thumb is that route components should be responsible for their own data fetching and rendering logic. The config should just specify which component to render for a given URL, not how to fetch the data or render the result.

Handle authentication and authorization

For routes that require authentication, it‘s useful to specify an auth property on the route object:

const routes = [
  {
    path: ‘/dashboard‘,
    component: Dashboard,
    auth: true,
  },
];

You can then handle the auth logic centrally via a specialized wrapper component or higher-order component. For example:

const AuthRoute = ({ component: Component, auth, ...rest }) => (
  <Route 
    {...rest}
    render={(props) => (
      auth ? (
        <Component {...props} />
      ) : (
        <Redirect to="/login" />  
      )
    )}
  />
);

This keeps your auth logic separated from your individual route components, which can greatly simplify maintenance over time.

Use a config for code splitting

As mentioned earlier, the route config is a perfect place to specify your code splitting strategy. By using dynamic imports for your route components, you can easily split your JavaScript bundle by route:

const routes = [
  {
    path: ‘/‘,
    component: () => import(‘./components/Home‘),
  },
  {
    path: ‘/blog‘,
    component: () => import(‘./components/Blog‘),
  },
];

This approach makes it dead simple to get the performance benefits of code splitting without littering your routing logic with a bunch of asynchronous component imports.

Render breadcrumbs from the route hierarchy

One neat UI feature you can build with the route config is automatic breadcrumbs. Since the config is a hierarchical data structure, it‘s easy to transform it into a corresponding hierarchy of breadcrumb links.

Here‘s a rough example of how you might implement this:

const Breadcrumbs = ({ routes }) => {
  const path = [];

  return (
    <ul>
      {routes.map((route, i) => {
        path.push(route.path);
        return (
          <li key={i}>
            <Link to={`/${path.join(‘/‘)}`}>{route.name}</Link>  
          </li>
        );
      })}
    </ul>
  );  
};

By mapping over the routes array and keeping track of the accumulated path, you can render a series of links that reflect the current position in the route hierarchy.

Performance considerations

One common concern with the route config pattern is performance. Will defining routes as objects introduce performance overhead compared to hardcoded <Route> elements?

The short answer is no. The process of mapping a config array to <Route> elements is fast and straightforward. In the vast majority of cases, any performance difference will be negligible.

The only scenario where you might see a performance hit is with very large route configs. If you have hundreds of routes, the time spent mapping over the config array can add up. However, even in these cases, the impact is typically minimal. And the benefits of centralized route configuration often outweigh the small performance trade-off.

One performance pitfall to watch out for is unnecessary re-renders when the route changes. By default, React Router will re-render all matching routes on every location change. This can lead to some subtle performance issues.

To avoid this, you can wrap your routes in a <Switch> component. <Switch> will only render the first matching route, which avoids the multiple-match issue. Alternatively, you can use the exact prop on your <Route> elements to ensure that only one route matches at a time.

Conclusion

For complex applications, the React Router route config is a powerful tool for maintaining a well-structured, performant codebase. By centralizing your routing logic, you gain:

• A clean separation of concerns between routing and rendering
• A high-level view of your app‘s overall structure
• The ability to enable advanced patterns like code splitting and server-side rendering

What‘s more, the route config naturally encourages a modular, componentized architecture. It pushes you to break your UI into reusable pieces that can be composed together declaratively.

If you‘re not yet using a centralized route config in your React Router code, I highly encourage you to give it a try. The initial setup can take a bit of work, but the long-term benefits are more than worth it. Your future self will thank you!