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Version: 6.x

Server rendering

This guide will cover how to server render your React Native app using React Native for Web and React Navigation. We'll cover the following cases:

  1. Rendering the correct layout depending on the request URL
  2. Setting appropriate page metadata based on the focused screen

Pre-requisites​

Before you follow the guide, make sure that your app already renders fine on server. To do that, you will need to ensure the following:

Rendering the app​

First, let's take a look at an example of how you'd do server rendering with React Native Web without involving React Navigation:

import { AppRegistry } from 'react-native-web';
import ReactDOMServer from 'react-dom/server';
import App from './src/App';

const { element, getStyleElement } = AppRegistry.getApplication('App');

const html = ReactDOMServer.renderToString(element);
const css = ReactDOMServer.renderToStaticMarkup(getStyleElement());

const document = `
  <!DOCTYPE html>
  <html style="height: 100%">
  <meta charset="utf-8">
  <meta httpEquiv="X-UA-Compatible" content="IE=edge">
  <meta
    name="viewport"
    content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1.00001, viewport-fit=cover"
  >
  ${css}
  <body style="min-height: 100%">
  <div id="root" style="display: flex; min-height: 100vh">
  ${html}
  </div>
`;

Here, ./src/App is the file where you have AppRegistry.registerComponent('App', () => App).

If you're using React Navigation in your app, this will render the screens rendered by your home page. However, if you have configured links in your app, you'd want to render the correct screens for the request URL on server so that it matches what'll be rendered on the client.

We can use the ServerContainer to do that by passing this info in the location prop. For example, with Koa, you can use the path and search properties from the context argument:

app.use(async (ctx) => {
  const location = new URL(ctx.url, 'https://example.org/');

  const { element, getStyleElement } = AppRegistry.getApplication('App');

  const html = ReactDOMServer.renderToString(
    <ServerContainer location={location}>{element}</ServerContainer>
  );

  const css = ReactDOMServer.renderToStaticMarkup(getStyleElement());

  const document = `
    <!DOCTYPE html>
    <html style="height: 100%">
    <meta charset="utf-8">
    <meta httpEquiv="X-UA-Compatible" content="IE=edge">
    <meta
      name="viewport"
      content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1.00001, viewport-fit=cover"
    >
    ${css}
    <body style="min-height: 100%">
    <div id="root" style="display: flex; min-height: 100vh">
    ${html}
    </div>
`;

  ctx.body = document;
});

You may also want to set the correct document title and descriptions for search engines, open graph etc. To do that, you can pass a ref to the container which will give you the current screen's options.

app.use(async (ctx) => {
  const location = new URL(ctx.url, 'https://example.org/');

  const { element, getStyleElement } = AppRegistry.getApplication('App');

  const ref = React.createRef<ServerContainerRef>();

  const html = ReactDOMServer.renderToString(
    <ServerContainer
      ref={ref}
      location={location}
    >
      {element}
    </ServerContainer>
  );

  const css = ReactDOMServer.renderToStaticMarkup(getStyleElement());

  const options = ref.current?.getCurrentOptions();

  const document = `
    <!DOCTYPE html>
    <html style="height: 100%">
    <meta charset="utf-8">
    <meta httpEquiv="X-UA-Compatible" content="IE=edge">
    <meta
      name="viewport"
      content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1.00001, viewport-fit=cover"
    >
    ${css}
    <title>${options.title}</title>
    <body style="min-height: 100%">
    <div id="root" style="display: flex; min-height: 100vh">
    ${html}
    </div>
`;

  ctx.body = document;
});

Make sure that you have specified a title option in your screens:

<Stack.Screen
  name="Profile"
  component={ProfileScreen}
  options={{ title: 'My profile' }}
/>

Handling 404 or other status codes​

When rendering a screen for an invalid URL, we should also return a 404 status code from the server.

First, we need to create a context where we'll attach the status code. To do this, place the following code in a separate file that we will be importing on both the server and client:

import * as React from 'react';

const StatusCodeContext = React.createContext();

export default StatusCodeContext;

Then, we need to use the context in our NotFound screen. Here, we add a code property with the value of 404 to signal that the screen was not found:

function NotFound() {
  const status = React.useContext(StatusCodeContext);

  if (status) {
    staus.code = 404;
  }

  return (
    <View>
      <Text>Oops! This URL doesn't exist.</Text>
    </View>
  );
}

You could also attach additional information in this object if you need to.

Next, we need to create a status object to pass in the context on our server. By default, we'll set the code to 200. Then pass the object in StatusCodeContext.Provider which should wrap the element with ServerContainer:

// Create a status object
const status = { code: 200 };

const html = ReactDOMServer.renderToString(
  // Pass the status object via context
  <StatusCodeContext.Provider value={status}>
    <ServerContainer ref={ref} location={location}>
      {element}
    </ServerContainer>
  </StatusCodeContext.Provider>
);

// After rendering, get the status code and use it for server's response
ctx.status = status.code;

After we render the app with ReactDOMServer.renderToString, the code property of the status object will be updated to be 404 if the NotFound screen was rendered.

You can follow a similar approach for other status codes too, for example, 401 for unauthorized etc.

Summary​

  • Use the location prop on ServerContainer to render correct screens based on the incoming request.
  • Attach a ref to the ServerContainer get options for the current screen.
  • Use context to attach more information such as status code.