rsnext/examples/with-react-intl/README.md

# Example app with [React Intl][]

This example app shows how to integrate [React Intl][] with Next.

## How to use

### Using `create-next-app`

Execute [`create-next-app`](https://github.com/zeit/next.js/tree/canary/packages/create-next-app) with [npm](https://docs.npmjs.com/cli/init) or [Yarn](https://yarnpkg.com/lang/en/docs/cli/create/) to bootstrap the example:

```bash
npm init next-app --example with-react-intl with-react-intl-app
# or
yarn create next-app --example with-react-intl with-react-intl-app
```

### Download manually

Download the example:

```bash
curl https://codeload.github.com/vercel/next.js/tar.gz/canary | tar -xz --strip=2 next.js-canary/examples/with-react-intl
cd with-react-intl
```

Install it and run:

```bash
npm install
npm run dev
# or
yarn
yarn dev
```

Deploy it to the cloud with [Vercel](https://vercel.com/import?filter=next.js&utm_source=github&utm_medium=readme&utm_campaign=next-example) ([Documentation](https://nextjs.org/docs/deployment)).

### Features of this example app

- Server-side language negotiation
- React Intl locale data loading via `pages/_document.js` customization
- React Intl integration with [custom App](https://github.com/zeit/next.js#custom-app) component
- `<IntlProvider>` creation with `locale`, `messages` props
- Default message extraction via `babel-plugin-react-intl` integration
- Translation management via build script and customized Next server

### Translation Management

This app stores translations and default strings in the `lang/` dir. This dir has `.messages/` subdir which is where React Intl's Babel plugin outputs the default messages it extracts from the source code. The default messages (`en.json` in this example app) is also generated by the build script. This file can then be sent to a translation service to perform localization for the other locales the app should support.

The translated messages files that exist at `lang/*.json` are only used during production, and are automatically provided to the `<IntlProvider>`. During development the `defaultMessage`s defined in the source code are used. To prepare the example app for localization and production run the build script and start the server in production mode:

```bash
$ npm run build
$ npm start
```

You can then switch your browser's language preferences to French and refresh the page to see the UI update accordingly.

### FormattedHTMLMessage support (react-intl pre-v4)

Out of the box, this example does not support the use of the `FormattedHTMLMessage` component on the server due to `DOMParser` not being present in a Node environment.
This functionality is deprecated and has been removed as of react-intl 4.0
If you still want to enable this feature, you should install a `DOMParser` implementation (e.g. `xmldom` or `jsdom`) and enable the polyfill in `server.js`:

```js
// Polyfill Node with `DOMParser` required by formatjs.
// See: https://github.com/zeit/next.js/issues/10533
const { DOMParser } = require('xmldom')
global.DOMParser = DOMParser
```

[react intl]: https://github.com/yahoo/react-intl

### Transpile react-intl

According to [react-intl docs](https://github.com/formatjs/react-intl/blob/53f2c826c7b1e50ad37215ce46b5e1c6f5d142cc/docs/Getting-Started.md#esm-build), react-intl and its underlying libraries must be transpiled to support older browsers (eg IE11). This is done by [next-transpile-modules](https://www.npmjs.com/package/next-transpile-modules) in next.config.js.