next-translate-zem v0.11.1

• 1. About the library
  • How does it work in Static / SSG pages?
• 2. Getting started without a custom server (○ Static, ● SSG)
  • Add to your project
  • Use translations in your pages
  • Add pages to .gitignore
• 3. Getting started with a custom server (λ Server)
  • Add to your project
  • Add i18nMiddleware to your custom server
  • Use translations in your pages
• 4. Create /locales directory with translations JSONs
• 5. Configuration
• 5. API
  • useTranslation
  • withTranslation
  • Trans Component
  • appWithI18n
  • DynamicNamespaces
  • i18nMiddleware
  • Link
  • Router
  • clientSideLang
• 7. Plurals
• 8. Use HTML inside the translation
• 9. Nested translations
• 10. How to change the language
• 11. Demos
  • Static site example
  • With custom server example

1. About the library

Tool to translate Next.js pages. There are two ways to work:

• Building pages before next build with the CLI (○ Static | ● SSG)
• Using a middleware in a custom server (λ Server)

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 in Static / SSG pages?

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 without a custom server (○ Static, ● SSG)

Add to your project

• yarn add next-translate

Note: For a Next.js version below than 9.3.0, use next-translate@0.9.0 or below

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 custom server (λ Server)

Add to your project

• yarn install next-translate

Note: For a Next.js version below than 9.3.0, use next-translate@0.9.0 or below

Add i18nMiddleware to your custom server

Using a custom 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 custom 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: ~614b

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: ~759b

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: ~1.5kb

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: ~4.7kb

This HOC is the way to wrap all your app under translations in the case that you are using a custom 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: ~4.1kb

The DynamicNamespaces component is useful to load dynamic namespaces, for example, in modals. This component works in both cases (static sites and with a custom 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: ~1.4kb

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

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)

Link

📦Size: ~11kb (next/link size included)

It is a wrapper of next/link that adds the current language at the beginning of the path, without to worry to add the language in every navigation. In order to change the language, you can pass the lang as props:

import Link from 'next-translate/Link'

// If the current language is 'en':

// -> Navigate to /en/some-path
<Link href="/some-path"><a>Navigate</a></Link>

 // -> Navigate to /es/route-in-spanish
<Link href="/route-in-spanish" lang="es"><a>Navigate</a></Link>

Props: Same props than next/link + only one additional prop:

• lang: <String> prop useful to navigate to a different language than the current one. The default value, if this prop is not provided, is the current language. So you don't need to worry about passing this prop for normal navigation.

Router

📦Size: ~10kb (next/router size included)

It is a wrapper of next/router when you can use the normal router of next.js, adding two extra methods:

• Router.pushI18n: It is exactly the same as Router.push, with the difference that it adds the current language at the beginning of the URL. In order to change the language, you can pass the lang into the options.
• Router.replaceI18n: It is exactly the same as Router.replace, with the difference that it adds the current language at the beginning of the URL. In order to change the language, you can pass the lang into the options.

import Router from 'next-translate/Router'

// If the current language is 'en':

// -> Navigate to /en/some-path
Router.pushI18n('/some-path')

// -> Navigate to /es/route-in-spanish
Router.pushI18n({ url: '/route-in-spanish', options: { lang: 'es' } })
// or
Router.pushI18n('/route-in-spanish', undefined, { lang: 'es' })

clientSideLang

📦Size: ~590b

Useful to get the language outside Components.

Example using a custom server:

import clientSideLang from 'next-translate/clientSideLang'

// ...

Page.getInitialProps({ req }) {
   const lang = req ? req.lang : clientSideLang()
  // ...
}

Or just for helpers:

import clientSideLang from 'next-translate/clientSideLang'

// ...

export function myClientSideHelper() {
  const lang = clientSideLang()
  // ...
}

It is not recommended to use the clientSideLang on the server-side directly because is stored in a global variable and it can cause some concurrency issues.

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 Link from 'next-translate/Link'
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={lng} key={lng}>
        {t(`layout:language-name-${lng}`)}
      </Link>
    )
  })
}

11. Demos

Static site example

• yarn install
• yarn example:static-site

With custom server example

• yarn install
• yarn example:with-server