Common i18n patterns in React

Following page describes the most common i18n patterns in React. It's a follow-up to tutorial with practical examples. See the API reference for detailed information about all components.

Macros

Using jsx macros is the most straightforward way how to translate your React components.

Trans handles translations of messages including variables and other React components:

import { Trans } from "@lingui/macro"

function render() {
  return (
    <>
      <h1><Trans>LinguiJS example</Trans></h1>
      <p><Trans>Hello <a href="/profile">{name}</a>.</Trans></p>
    </>
  );
}

You don't need anything special to use Trans inside your app (except of wrapping the root component in I18nProvider).

Choosing between generated and explicit ID

Using generated IDs provides more scalability and gives a better developer experience. On the other hand, explicit IDs for phrases make it easier to identify phrases out of context and to track where they're used. IDs usually follow a naming scheme that includes where the phrase is used.

Using ID generated from message

With Trans

In the example code above, the content of Trans is transformed into a message in MessageFormat syntax. By default, this message is used for generating the ID. Considering the example above, the catalog would be fulfilled by these entries:

const catalog = [
  {
    id: "uxV9Xq",
    message: "LinguiJS example",
  },
  {
    id: "9/omjw",
    message: "Hello <0>{name}</0>.",
  },
]

With t

In the following example, the message Image caption will be extracted and used to create an ID.

import { t } from "@lingui/macro"

export default function ImageWithCaption() {
   return <img src="..." alt={t`Image caption`} />
}

Providing a context for a message

The same text elements with different contexts are extracted with different IDs. For example, if the word "right" uses the following two definitions in two different locations, the word is translated differently and merged back into the application as different translation entries.

• correct as in "you are right"
• direction as in "turn right"

If the same text elements meet the following conditions, the text elements are extracted only once and use the same ID.

import { Trans } from "@lingui/macro";
<Trans context="direction">right</Trans>;
<Trans context="correctness">right</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id={"d1wX4r"} message="right" />;
<Trans id={"16eaSK"} message="right" />;

Using custom ID

With Trans

If you're using custom IDs in your project, add id prop to i18n components:

import { Trans } from "@lingui/macro"

function render() {
  return (
    <>
      <h1><Trans id="msg.header">LinguiJS example</Trans></h1>
      <p><Trans id="msg.hello">Hello <a href="/profile">{name}</a>.</Trans></p>
    </>
  );
}

Messages msg.header and msg.hello will be extracted with default values LinguiJS example and Hello <0>{name}</0>..

With t

If you're using custom IDs in your project, call t with a message descriptor object and pass ID as id prop:

import { t } from "@lingui/macro"

export default function ImageWithCaption() {
   return <img src="..." alt={t({id: 'msg.caption', message: `Image caption`})} />
}

Message msg.caption will be extracted with default value Image caption.

For all other js macros (plural, select, selectOrdinal, use them inside t macro to pass ID (in this case, 'msg.caption').

import { t, plural } from "@lingui/macro"

export default function ImageWithCaption({ count }) {
   return (
      <img src="..." alt={t({id: 'msg.caption', message: plural(count, {
         one: "# image caption",
         other: "# image captions",
      })})} />
   )
}

Element attributes and string-only translations

Sometimes you can't use Trans component, for example when translating element attributes:

<img src="..." alt="Image caption" />

In such case you need to use t macro to wrap message. t is equivalent for Trans, plural is equivalent to Plural.

import { t } from "@lingui/macro"

export default function ImageWithCaption() {
   return <img src="..." alt={t`Image caption`} />
}

Translations outside React components

Another common pattern is when you need to access translations outside React components, for example inside redux-saga. You can use t macro outside React context as usual:

import { t } from "@lingui/macro"

export function alert() {
    // use t as if you were inside a React component
    alert(t`...`)
}

Lazy translations

Messages don't have to be declared at the same code location where they're displayed. Tag a string with the defineMessage macro, and you've created a "message descriptor", which can then be passed around as a variable, and can be displayed as a translated string by passing its id to Trans as its id prop:

import { defineMessage, Trans } from "@lingui/macro"

const favoriteColors = [
   defineMessage({message: "Red"}),
   defineMessage({message: "Orange"}),
   defineMessage({message: "Yellow"}),
   defineMessage({message: "Green"}),
]

export default function ColorList() {
   return (
      <ul>
         {favoriteColors.map(color => (
            <li><Trans id={color.id}/></li>
         ))}
      </ul>
   )
}

Or to render the message descriptor as a string-only translation, just pass it to the i18n._() method:

import { i18n } from "@lingui/core"
import { defineMessage } from "@lingui/macro"

const favoriteColors = [
   defineMessage({message: "Red"}),
   defineMessage({message: "Orange"}),
   defineMessage({message: "Yellow"}),
   defineMessage({message: "Green"}),
]

export function getTranslatedColorNames() {
   return favoriteColors.map(
      color => i18n._(color)
   )
}

Passing messages as props

It's often convenient to pass messages around as component props, for example as a "label" prop on a button. The easiest way to do this is to pass a Trans element as the prop:

import { Trans } from "@lingui/macro"

export default function FancyButton(props) {
   return <button>{props.label}</button>
}

export function LoginLogoutButtons(props) {
   return <div>
      <FancyButton label={<Trans>Log in</Trans>} />
      <FancyButton label={<Trans>Log out</Trans>} />
   </div>
}

If you need the prop to be displayed as a string-only translation, you can pass a message tagged with the t macro:

import { t } from "@lingui/macro"

export default function ImageWithCaption(props) {
   return <img src="..." alt={props.caption} />
}

export function HappySad(props) {
   return <div>
      <ImageWithCaption caption={t`I'm so happy!`} />
      <ImageWithCaption caption={t`I'm so sad.`} />
   </div>
}

Picking a message based on a variable

Sometimes you need to pick between different messages to display, depending on the value of a variable. For example, imagine you have a numeric "status" code that comes from an API, and you need to display a message representing the current status.

A simple way to do this, is to make an object that maps the possible values of "status" to message descriptors (tagged with the defineMessage macro), and render them as needed with lazy translation:

import { defineMessage } from "@lingui/macro";
import { i18n } from "@lingui/core";

const statusMessages = {
   ['STATUS_OPEN']: defineMessage({message: "Open"}),
   ['STATUS_CLOSED']: defineMessage({message: "Closed"}),
   ['STATUS_CANCELLED']: defineMessage({message: "Cancelled"}),
   ['STATUS_COMPLETED']: defineMessage({message: "Completed"}),
}

export default function StatusDisplay({ statusCode }) {
   return <div>{i18n._(statusMessages[statusCode])}</div>
}