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Common i18n patterns in React

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

Macros​

Using jsx macros is the most straightforward way 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).

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 the useLingui() hook with the msg macro.

import { msg } from "@lingui/macro";
import { useLingui } from "@lingui/react";

export default function ImageWithCaption() {
  const { _ } = useLingui();

  return <img src="..." alt={_(msg`Image caption`)} />;
}

Translations outside React components​

Sometimes, you may need to access translations outside React components, which is another common pattern. You can use t macro outside React context as usual:

import { t } from "@lingui/macro";

export function showAlert() {
  alert(t`...`);
}
caution

When you use t macro (and plural, select, selectOrdinal), it uses a global i18n instance. While this generally works, there are situations, like in server-side rendering (SSR) applications, where it may not be the best fit.

For better control and flexibility, it's a good idea to avoid the global i18n instance and instead use a specific instance tailored to your needs.

import { msg } from "@lingui/macro";
import { I18n } from "@lingui/core";

export function showAlert(i18n: I18n) {
  alert(t(i18n)`...`);
}

function MyComponent() {
  // get i18n instance from React Context
  const { i18n } = useLingui();

  // pass instance outside
  showAlert(i18n);
}
note

All js macros such as t plural, select, selectOrdinal cannot be used on the module level.

import { t } from "@lingui/macro";

// ❌ Bad! This won't work because the `t` macro is used at the module level.
// The `t` macro returns a string, and once this string is assigned, it won't react to locale changes.
const colors = [t`Red`, t`Orange`, t`Yellow`, t`Green`];

// ✅ Good! Every time the function is executed, the `t` macro will be re-executed as well,
// and the correctly translated color labels will be returned.
function getColors() {
  return [t`Red`, t`Orange`, t`Yellow`, t`Green`];
}

There is an ESLint Rule designed to check for this misuse.

A better option would be to use the Lazy Translations pattern described in the following paragraph.

Lazy Translations​

You don't need to declare messages at the same code location where they are displayed. Tag a string with the msg 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 { msg } from "@lingui/macro";
import { Trans } from "@lingui/react";

const favoriteColors = [msg`Red`, msg`Orange`, msg`Yellow`, msg`Green`];

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

Note that we import <Trans> component from @lingui/react, because we want to use the runtime Trans component here, not the (compile-time) macro.

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

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

const favoriteColors = [msg`Red`, msg`Orange`, msg`Yellow`, msg`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 msg macro:

import { msg } from "@lingui/macro";
import { useLingui } from "@lingui/react";

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

export function HappySad(props) {
  const { _ } = useLingui();

  return (
    <div>
      <ImageWithCaption caption={_(msg`I'm so happy!`)} />
      <ImageWithCaption caption={_(msg`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 create an object that maps the possible values of "status" to message descriptors (tagged with the msg macro), and render them as needed with deferred translation:

import { msg } from "@lingui/macro";
import { useLingui } from "@lingui/react";

const statusMessages = {
  ["STATUS_OPEN"]: msg`Open`,
  ["STATUS_CLOSED"]: msg`Closed`,
  ["STATUS_CANCELLED"]: msg`Cancelled`,
  ["STATUS_COMPLETED"]: msg`Completed`,
};

export default function StatusDisplay({ statusCode }) {
  const { _ } = useLingui();
  return <div>{_(statusMessages[statusCode])}</div>;
}

Memoization pitfall​

In the following contrived example, we document how a welcome message will or will not be updated when locale changes.

The documented behavior may not be intuitive at first, but it is expected, because of how useMemo dependencies work.

To avoid bugs with stale translations, use the _ function returned from useLingui: it is safe to use with memoization because its reference changes whenever the Lingui context updates. We are open to accepting solutions to make working with the Lingui context easier.

Keep in mind that useMemo is primarily a performance optimization tool in React. Because of this, there might be no need to memoize your translations. Additionally, this issue is not present when using the Trans component which we recommend to use when possible.

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

const welcomeMessage = msg`Welcome!`;

// ❌ Bad! This code won't work
export function Welcome() {
  const buggyWelcome = useMemo(() => {
    return i18n._(welcomeMessage);
  }, []);

  return <div>{buggyWelcome}</div>;
}

// ❌ Bad! This code won't work either because the reference to i18n does not change
export function Welcome() {
  const { i18n } = useLingui();

  const buggyWelcome = useMemo(() => {
    return i18n._(welcomeMessage);
  }, [i18n]);

  return <div>{buggyWelcome}</div>;
}

// ✅ Good! `useMemo` has i18n context in the dependency
export function Welcome() {
  const linguiCtx = useLingui();

  const welcome = useMemo(() => {
    return linguiCtx.i18n._(welcomeMessage);
  }, [linguiCtx]);

  return <div>{welcome}</div>;
}

// 🤩 Better! `useMemo` consumes the `_` function from the Lingui context
export function Welcome() {
  const { _ } = useLingui();

  const welcome = useMemo(() => {
    return _(welcomeMessage);
  }, [_]);

  return <div>{welcome}</div>;
}