Tutorial of using react-i18next alongside with documentations can be found here.

When first encounter Trans component, there are many questions: "what are these indexed tags?", "how to get numbers correctly?", "when actually we need to use this component?". Let's dive in.

Table of contents

• When to use;
• Indexed tags;
• Plurals;

When to use

Trans component allows to translate whole JSX tree in one translation: so when the element contains multiple tags and we don't want to break it to small pieces of translation, we can refer to this component.

Indexed tags

Let's say we want output like this:

//MyComponent.jsx

const name='mary';

export default function MyComponent () {

const [state, setState] = useState(1);

  return (
  <Trans i18nKey="userGreetings" count={state}>
    Hello, <strong title={t('nameTitle')}>{{name}}</strong>! You have chosen {{state}} products. <a href="/cart">Go to shopping cart</a>.
  </Trans>
  )
}

Now, we have to add this string to translation. However, first we need to know what to put instead of html tags. There are several ways to know these numbers:

debug=true and console

The easiest way is to look in console for missing key output (for this to work debug: true must be in i18n.init({}) options):

And we can just copy that string and paste it in translation:

//translationEn.js

const translation = {
  nameTitle: "Your name",
  userGreetings: "Hello, <1>{{name}}</1>! You have chosen {{count}} product. <5>Go to shopping cart</5>."
}

export default translation;

React Developer Tools

We can inspect <Trans> component in devtools:

Here, we have indexes for each child in props.children array.

Understand how indexes are generated

Children are divided by these rules:

• plain string;
• object, that's used for interpolation;
• element with its' own children. The children support the same rules. Thus, there can be nested elements in one Trans component.

Let's look at our example:

From this string:

Hello, <strong title={t('nameTitle')}>{{name}}</strong>! You have chosen {{state}} products. <a href="/cart">Go to shopping cart</a>.

Children of Trans node:

0. 'Hello' - just string;
1. strong element with a child-object: {name: 'mary'}
2. 'You have chosen' - just string;
3. {state} - object;
4. ' products. ' - just string
5. a element with a child-string: 'Go to shopping cart'
6. '.' - just string

We come to this:

Hello, <1>{{name}}</1>! You have chosen {{count}} product. <5>Go to shopping cart</5>.

Plurals

We can actually set our translation like this:

  userGreetings_one: "Hello, <1>{{name}}</1>! you have chosen {{count}} product. <5>Go to shopping cart</5>.",
  userGreetings_other: "Hello, <1>{{name}}</1>! you have chosen {{count}} products. <5>Go to shopping cart</5>."

The difference is in plural form of product.

We need prop count in Trans component:

<Trans i18nKey="userGreetings" count={state}>...