next-translate v2.6.2

• 1. About the library
  • How does it work statically?
• 2. Getting started (static site)
  • Add to your project
  • Use translations in your pages
  • Add pages to .gitignore
• 3. Getting started (with a server)
  • Add to your project
  • Add i18nMiddleware to your server
  • Use translations in your pages
• 4. Create /locales directory with translations JSONs
• 5. Configuration
• 5. API
  • useTranslation
  • withTranslation
  • Trans Component
  • appWithI18n
  • DynamicNamespaces
  • i18nMiddleware
• 7. Plurals
• 8. Use HTML inside the translation
• 9. Nested translations
• 10. How to change the language
• 11. Demos
  • Static site example
  • With server example

1. About the library

Tool to translate Next.js pages without the need of a server (static i18n pages generator).

The main goal of this library is to keep the translations as simple as possible in a Next.js environment.

This library is very tiny and tree shakable.

How does it work statically?

Instead of working on /pages directory to write our pages, we are going to generate this folder before building the app, an each page will have all the necessary translations from the locale.

Imagine that we are working in an alternative /pages_ to build our pages:

/pages_

.
├── about.js
├── index.js
└── nested
    └── index.js

Then, when we build the app, this /pages structure is going to be automatically generated:

.
├── about.js
├── ca
│   ├── about.js
│   ├── index.js
│   └── nested
│       └── index.js
├── en
│   ├── about.js
│   ├── index.js
│   └── nested
│       └── index.js
├── es
│   ├── about.js
│   ├── index.js
│   └── nested
│       └── index.js
├── index.js
└── nested
    └── index.js

Each page and its components can consume the translations with the useTranslation hook.

const { t, lang } = useTranslation()
const title = t('common:title')

2. Getting started (static site)

Add to your project

• yarn add next-translate

In your package.json:

"scripts": {
  "dev": "next-translate && next dev",
  "build": "next-translate && next build",
  "start": "next start"
}

Use translations in your pages

You should create your namespaces files inside /locales. See how to do it

For a static site you should add a configuration file i18n.json in the root of the project. Each page should have its namespaces. Take a look to the config section for more details.

{
  "allLanguages": ["en", "ca", "es"],
  "defaultLanguage": "en",
  "currentPagesDir": "pages_",
  "finalPagesDir": "pages",
  "localesPath": "locales",
  "pages": {
    "*": ["common"],
    "/": ["home", "example"],
    "/about": ["about"]
  }
}

Then, use the translations in the page and its components:

import useTranslation from 'next-translate/useTranslation'
// ...
const { t, lang } = useTranslation()
const example = t('common:variable-example', { count: 42 })
// ...
return <div>{example}</div>

⚠️ Important: _app.js, _document.js and _error.js are not going to be wrapped with the translations context, so it's not possible to direclty translate these files. In order to do that, you should take a look at DynamicNamespaces to load the namespaces dynamically.

Add /pages to .gitignore

/pages directory is going to be generated every time based on /pages_, so it's not necessary to track it in git.

3. Getting started (with a server)

Add to your project

• yarn install next-translate

Add i18nMiddleware to your server

Using a server you should add the i18nMiddleware in order to add the language and allow to render the pages behind the /{lang} prefix.

const express = require('express')
const next = require('next')
const i18nMiddleware = require('next-translate/i18nMiddleware').default
const i18nConfig = require('./i18n')

const dev = process.env.NODE_ENV !== 'production'
const app = next({ dev })
const handle = app.getRequestHandler()
const server = express()
const PORT = parseInt(process.env.PORT, 10) || 3000

// You should add this middleware
server.use(i18nMiddleware(i18nConfig))

server.get('*', handle)

module.exports = app
  .prepare()
  .then(() =>
    server.listen(PORT, err => {
      if (err) throw err
      console.log(`> Ready on http://localhost:${PORT}`)
    })
  )
  .catch(console.error)

Where the config is in the root path as i18n.js:

module.exports = {
  allLanguages: ['en', 'ca', 'es'],
  defaultLanguage: 'es',
  redirectToDefaultLang: true,
  loadLocaleFrom: (lang, ns) =>
    import(`./locales/${lang}/${ns}.json`).then(m => m.default),
  pages: {
    '/': ['common', 'home'],
    '/more-examples': ['common', 'more-examples'],
    '/more-examples/dynamic-namespace': ['common'],
  },
}

It's important to move the configuration in another file because in the next step also you are going to use it.

Use translations in your pages

You should create your namespaces files inside /locales. See how to do it

Using a server, you should pass the configuration into the appWithI18n wrapper of your app. Each page should have its namespaces. Take a look to the config section for more details.

_app.js

import appWithI18n from 'next-translate/appWithI18n'
import i18nConfig from '../i18n'

function MyApp({ Component, pageProps }) {
  return <Component {...pageProps} />
}

export default appWithI18n(MyApp, i18nConfig)

Now, use translations in the page and its components:

import useTranslation from 'next-translate/useTranslation'
// ...
const { t, lang } = useTranslation()
const example = t('common:variable-example', { count: 42 })
// ...
return <div>{example}</div>

4. Create /locales directory with translations JSONs

The locales directory should be like this:

/locales

.
├── ca
│   ├── common.json
│   └── home.json
├── en
│   ├── common.json
│   └── home.json
└── es
    ├── common.json
    └── home.json

Each filename matches the namespace, while each file content should be similar to this:

{
  "title": "Hello world",
  "variable-example": "Using a variable {{count}}"
}

In order to use each translation in the project, use the translation id composed by namespace:key(ex: common:variable-example).

5. Configuration

6. API

useTranslation

📦Size: ~1.5kb

This hook is the recommended way to use translations in your pages / components.

• Input: void
• Output: Object { t: Function, lang: string }

Example:

import React from 'react'
import useTranslation from 'next-translate/useTranslation'

export default function Description() {
  const { t, lang } = useTranslation()
  const title = t('title')
  const description = t`common:description` // also works as template string
  const example = t('common:example', { count: 3 }) // and with query params

  return (
    <>
      <h1>{title}</h1>
      <p>{description}</p>
      <p>{example}</p>
    <>
  )
}

The t function:

• Input:
  • i18nKey: string (namespace:key)
  • query: Object (example: { name: 'Leonard' })
• Output: string

withTranslation

📦Size: ~2.5kb

It's an alternative to useTranslation hook, but in a HOC for these components that are no-functional.

The withTranslation HOC returns a Component with an extra prop named i18n (Object { t: Function, lang: string }).

Example:

import React from 'react'
import withTranslation from 'next-translate/withTranslation'

class Description extends React.Component {
  render() {
    const { t, lang } = this.props.i18n
    const description = t('common:description')

    return <p>{description}</p>
  }
}

export default withTranslation(NoFunctionalComponent)

Trans Component

📦Size: ~5kb

Sometimes we need to do some translations with HTML inside the text (bolds, links, etc). The Trans component is exactly what you need for this. We recommend to use this component only in this case, for other cases we highly recommend the usage of useTranslation hook instead.

Example:

// The defined dictionary enter is like:
// "example": "<0>The number is <1>{{count}}</1></0>",
<Trans
  i18nKey="common:example"
  components={[<Component />, <b className="red" />]}
  values={{ count: 42 }}
/>

• Props:
  • i18nKey - string - key of i18n entry (namespace:key)
  • components - Array - Each index correspont to the defined tag <0>/<1>.
  • values - Object - query params

appWithI18n

📦Size: ~10kb

This HOC is the way to wrap all your app under translations in the case that you are using a server. This method should not be used in a static site. This HOC adds logic to the getInitialProps to download the necessary namespaces in order to use it in your pages.

Example:

_app.js

import appWithI18n from 'next-translate/appWithI18n'
import i18nConfig from '../i18n'

function MyApp({ Component, pageProps }) {
  return <Component {...pageProps} />
}

export default appWithI18n(MyApp, i18nConfig)

See more details about the config that you can use.

DynamicNamespaces

📦Size: ~13kb

The DynamicNamespaces component is useful to load dynamic namespaces, for example, in modals. This component works in both cases (static sites and with a server).

Example:

import React from 'react'
import Trans from 'next-translate/Trans'
import DynamicNamespaces from 'next-translate/DynamicNamespaces'

export default function ExampleWithDynamicNamespace() {
  return (
    <DynamicNamespaces
      dynamic={(lang, ns) =>
        import(`../../locales/${lang}/${ns}.json`).then(m => m.default)
      }
      namespaces={['dynamic']}
      fallback="Loading..."
    >
      {/* ALSO IS POSSIBLE TO USE NAMESPACES FROM THE PAGE */}
      <h1>
        <Trans i18nKey="common:title" />
      </h1>

      {/* USING DYNAMIC NAMESPACE */}
      <Trans i18nKey="dynamic:example-of-dynamic-translation" />
    </DynamicNamespaces>
  )
}

Remember that ['dynamic'] namespace should not be listed on pages configuration:

 pages: {
    '/my-page': ['common'], // only common namespace
  }

i18nMiddleware

📦Size: ~4kb

This middleware is to use translations behind a server. You should add this middleware in your custom server:

const i18nMiddleware = require('next-translate/i18nMiddleware').default
const i18nConfig = require('./i18n')

// ...
server.use(i18nMiddleware(i18nConfig))

See more details about the config that you can use.

Props:

• dynamic - Function - Generic dynamic import of all namespaces (mandatory).
• namespaces - Array - List of namespaces to load dynamically (mandatory).
• fallback - Any - Fallback to render meanwhile namespaces are loading (default: null)

7. Plurals

You can define plurals this way:

{
  "plural-example": "This is singular because the value is {{count}}",
  "plural-example_0": "Is zero because the value is {{count}}",
  "plural-example_2": "Is two because the value is {{count}}",
  "plural-example_plural": "Is in plural because the value is {{count}}"
}

Example:

function PluralExample() {
  const [count, setCount] = useState(0)
  const { t } = useTranslation()

  useEffect(() => {
    const interval = setInterval(() => {
      setCount(v => (v === 5 ? 0 : v + 1))
    }, 1000)

    return () => clearInterval(interval)
  }, [])

  return <p>{t('namespace:plural-example', { count })}</p>
}

Result:

*Note: Only works if the name of the variable is {{count}}.*

8. Use HTML inside the translation

You can define HTML inside the translation this way:

{
  "example-with-html": "<0>This is an example <1>using HTML</1> inside the translation</0>"
}

Example:

import Trans from 'next-translate/Trans'
// ...
const Component = (props) => <p {...props} />
// ...
<Trans
  i18nKey="namespace:example-with-html"
  components={[<Component />, <b className="red" />]}
/>

Rendered result:

<p>This is an example <b class="red">using HTML</b> inside the translation</p>

Each index of components array corresponds with <index></index> of the definition.

In the components array it's not necessary to pass the children of each element. Children will be calculed.

9. Nested translations

In the namespace is possible to define nested keys like:

{
  "nested-example": {
    "very-nested": {
      "nested": "Nested example!"
    }
  }
}

In order to use it, you should use "." as id separator:

t`namespace:nested-example.very-nested.nested`

10. How to change the language

In order to change the current language you don't need anything of this library, you can do it directly with the next navigation:

• https://nextjs.org/learn/basics/navigate-between-pages

The only thing to remember, is to navigate with the /lang/ on front.

One example of a possible ChangeLanguage component:

import React from 'react'
import useTranslation from 'next-translate/useTranslation'
import i18nConfig from '../i18n.json'

const { allLanguages } = i18nConfig

function ChangeLanguage() {
  const { t, lang } = useTranslation()

  return allLanguages.map(lng => {
    if (lng === lang) return null

    // Or you can attach the current pathame at the end
    // to keep the same page
    return (
      <Link href={`/${lang}`} key={lng}>
        {t(`layout:language-name-${lng}`)}
      </Link>
    )
  })
}

11. Demos

Static site example

• yarn install
• yarn example:static-site

With server example

• yarn install
• yarn example:with-server