Next.js + react-router

This repo documents an attempt of using Next.js (preserving native SSR features) with the following setup:

• Single entry point (like Create React App and Hops). No file system-based routing
• react-router as only routing system

This document is available as:

• GitHub repository
• dev.to post

Disclaimers

• Next.js team strongly advises against this approach.
• This experiment was carried out at the times of Next.js v9.3: the framework has changed a lot since then.

Part one, basic setup

1 - Install Next.js

Relevant repo commit.

Install NextJS as usual and create the single entry point file at pages/index.js.

2 - Redirect all requests to single entrypoint

Relevant repo commit.

In order to skip file system-based routing, we'll configure a custom Next.js server to forward all the requests to our single entrypoint.

We'll use Next.js Server.render method to render and serve the entrypoint.

// server.js
const express = require('express');
const nextJS = require('next');

async function start() {
  const dev = process.env.NODE_ENV !== 'production';
  const app = nextJS({dev});
  const server = express();
  await app.prepare();

  // Redirect all requests to main entrypoint pages/index.js
  server.get('/*', async (req, res, next) => {
    try {
      app.render(req, res, '/');
    } catch (e) {
      next(e);
    }
  });

  server.listen(3000, err => {
    if (err) throw err;
    console.log(`> Ready on http://localhost:3000`);
  });
}

start();

Run the dev server, and the entrypoint page at pages/index.js should be served as response for any requested url.

3 - Introduce react-router

Relevant repo commit.

In order to get different responses according to the requested url we need a routing system.

We'll use react-router (see it's docs about SSR) and wrap the application with a StaticRouter or a BrowserRouter based on the environment application environment (server or browser).

Install react-router and react-router-dom:

npm i react-router react-router-dom -S

...and update the pages/index.js entrypoint to use some Link and Route components from react-router-dom (see repo).

Let's now declare a withReactRouter HOC to wrap the application with the proper router:

// next/with-react-router.js
import React from 'react';
import {BrowserRouter} from 'react-router-dom';
const isServer = typeof window === 'undefined';

export default App => {
  return class AppWithReactRouter extends React.Component {
    render() {
      if (isServer) {
        const {StaticRouter} = require('react-router');
        return (
          <StaticRouter
            location={this.props.router.asPath}
          >
            <App {...this.props} />
          </StaticRouter>
        );
      }
      return (
        <BrowserRouter>
          <App {...this.props} />
        </BrowserRouter>
      );
    }
  };
};

...and wrap the application with withReactRouter HOC:

// pages/_app.js
import App, {Container} from 'next/app';
import React from 'react';
import withReactRouter from '../next/with-react-router';

class MyApp extends App {
  render() {
    const {Component, pageProps} = this.props;
    return (
      <Container>
        <Component {...pageProps} />
      </Container>
    );
  }
}

export default withReactRouter(MyApp);

Run the dev server, and you should be able to see your routes live and server side rendered.

Part two, context information

One of my favourite react-router features consists of the possibility of adding context information during the rendering phase and returning server side responses based on the information collected into the context object.

This enables client side code to take control of the responses returned by the node server like returning a HTTP 404 instead of a "not found page" or returning a real HTTP 302 redirect instead of a client side one.

In order to achieve this behaviour we have to configure Next.js to do the following:

1. render the requested page providing a context object to the app router
2. check whether context object was mutated during the rendering process
3. decide whether to return the rendered page or do something else based on context object

4 - Provide context object to the router

Relevant repo commit.

We'll inject an empty context object into Express' req.local object and make it available to the router application via React Context.

Let's inject context object into Express' req.local object:

// server.js
server.get('/*', async (req, res, next) => {
  try {
+   req.locals = {};
+   req.locals.context = {};
    app.render(req, res, '/');

Next.js provides a req and res objects as props of getInitialProps static method. We'll fetch req.originalUrl and req.locals.context and handle it over to the static router.

// next/with-react-router.js
  return class AppWithReactRouter extends React.Component {
+   static async getInitialProps(appContext) {
+     const {
+       ctx: {
+         req: {
+           originalUrl,
+           locals = {},
+         },
+       },
+     } = appContext;
+     return {
+       originalUrl,
+       context: locals.context || {},
+     };
+   }

  // Code omitted
          <StaticRouter
-           location={this.props.router.asPath}
+           location={this.props.originalUrl}
+           context={this.props.context}
          >

5 - Separate rendering and response

Relevant repo commit.

Since we want to provide extra server behaviours based on req.locals.context in-between SSR and server response, Next.js Server.render falls short of flexibility.

We'll re-implement Server.render in server.js using Next.js Server.renderToHTML and Server.sendHTML methods.

Please note that some code was omitted. Refer to the source code for the complete implementation.

// server.js
  server.get('/*', async (req, res, next) => {
    try {
+     // Code omitted

      req.locals = {};
      req.locals.context = {};
-     app.render(req, res, '/');
+     const html = await app.renderToHTML(req, res, '/', {});
+
+     // Handle client redirects
+     const context = req.locals.context;
+     if (context.url) {
+       return res.redirect(context.url)
+     }
+
+     // Handle client response statuses
+     if (context.status) {
+       return res.status(context.status).send();
+     }
+
+     // Code omitted
+     app.sendHTML(req, res, html);
    } catch (e) {

Before sending the response with the rendered HTML to the client, we now check the context object and redirect or return a custom HTTP code, if necessary.

In order to try it out, update the pages/index.js entrypoint to make use of <Redirect> and <Status> components and start the dev server.

Summary

We showed how it's be possible to setup Next.js take full advantage of react-router, enabling single entrypoint approach and fully preserving SSR.

In order to do so we:

1. Redirected all server requests to a single entrypoint
2. Wrapped the application (using HOC) with the proper react-router router
3. Injected req server object with a locals.context object
4. Provided HOC wrapper with req.locals.context and req.originalUrl
5. Extended next.js Server.render to take into account req.locals.context before sending HTML

The re-implementation of Server.render in userland code is the most disturbing part of it, but it might be made unnecessary by extending a bit Server.render API in Next.js.

Results

react-router rendered server side

react-router's <Route> components get statically rendered on the server based on received req.originalUrl url.

HTTP 302 redirect triggered by client code

When server rendering process encounters <Redirect from="/people/" to="/users/" /> component, the server response will return an HTTP 302 response with the expected Location header.

HTTP 404 triggered by client code

When server rendering process encounters <Status code={404}/> component, the server response returns an HTTP response with the expected status code.

Further consideration

I'm sure this setup is way far from being optimal. I'll be happy take into account any suggestions, feedbacks, improvements, ideas.

Issues

• Static pages not being exported
• Dev mode cannot build requested route on demand
• getInitialProps not implemented