Angular i18n built-in support

Introduction

Angular i18n helps you make your app speak different languages easily. It changes text based on the user's language.

You want your app to show text in English, Spanish, or other languages.

You need to support users from different countries with their own language.

You want to prepare your app for future languages without big changes.

You want to keep your app accessible and friendly for everyone.

Syntax

Angular

<div i18n>Welcome to our app!</div>

<!-- In TypeScript -->
import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html'
})
export class AppComponent {}

The i18n attribute marks text for translation.

Angular extracts these texts to create translation files.

Examples

Simple text marked for translation.

Angular

<h1 i18n>Home Page</h1>

Text with a custom translation ID for clarity.

Angular

<button i18n="@@saveBtn">Save</button>

Text with dynamic content using Angular pipes.

Angular

<p i18n>Today is {{ today | date }}</p>

Sample Program

This simple component shows how to mark text for translation using i18n. When you extract and add translations, Angular will replace the text based on the user's language.

Angular

/* app.component.html */
<div i18n>Hello, welcome to our app!</div>

/* app.component.ts */
import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html'
})
export class AppComponent {
  today = new Date();
}

/* Usage: Run Angular i18n extraction and build with translations to see text change */

Important Notes

Use the Angular CLI command ng extract-i18n to get translation files.

Translations are stored in XLIFF or other supported formats.

You need to build your app separately for each language to serve translated versions.

Summary

Angular i18n uses the i18n attribute to mark text for translation.

Extract translations with Angular CLI and provide translated files.

Build your app for each language to serve users in their language.

Practice

1. What is the primary purpose of the i18n attribute in Angular templates?

easy

A. To mark text for translation into different languages

B. To apply CSS styles conditionally

C. To bind data to the component

D. To define event handlers for user actions

Solution

1. Step 1: Understand the role of i18n in Angular

   The i18n attribute is used to identify text in templates that should be translated for internationalization.

2. Step 2: Compare with other options

   The other options relate to styling, data binding, and events, which are unrelated to translation.

3. Final Answer:

   To mark text for translation into different languages -> Option A

4. Quick Check:

   i18n attribute = mark text for translation [OK]

Hint: Remember: i18n means internationalization, so it marks text for translation [OK]

Common Mistakes:

• Confusing i18n with data binding syntax
• Thinking i18n applies styles or events
• Assuming i18n is a directive instead of an attribute

2. Which of the following is the correct syntax to mark a paragraph for translation in Angular?

easy

A. Hello, welcome!

B. Hello, welcome!

C. Hello, welcome!

D. Hello, welcome!

Solution

1. Step 1: Recall Angular i18n attribute usage

   The i18n attribute is added directly to the element without brackets or asterisk.

2. Step 2: Analyze each option

   Hello, welcome!

   uses i18n correctly.

   Hello, welcome!

   uses property binding syntax which is incorrect.

   Hello, welcome!

   uses structural directive syntax which is invalid here.

   Hello, welcome!

   uses a non-existent attribute i18n-text.

3. Final Answer:

   <p i18n>Hello, welcome!</p> -> Option D

4. Quick Check:

   Use plain i18n attribute without brackets or asterisk [OK]

Hint: Use plain i18n attribute on elements, no brackets or asterisks [OK]

Common Mistakes:

• Using property binding syntax [i18n]
• Using structural directive syntax *i18n
• Inventing attributes like i18n-text

3. Given this Angular template snippet:

<h1 i18n>Welcome, {{ userName }}!</h1>

What will be the output if userName is 'Alice' and the app is built with English locale?

medium

A. Welcome, !

B. Welcome, {{ userName }}!

C. Welcome, Alice!

D. Error: Missing translation

Solution

1. Step 1: Understand interpolation with i18n

   The i18n attribute marks the text for translation but Angular still processes interpolation expressions like {{ userName }}.

2. Step 2: Consider the locale and variable value

   With English locale and userName as 'Alice', the text renders with the variable replaced by 'Alice'.

3. Final Answer:

   Welcome, Alice! -> Option C

4. Quick Check:

   i18n with interpolation outputs translated text with variables replaced [OK]

Hint: i18n marks text, interpolation fills variables at runtime [OK]

Common Mistakes:

• Thinking interpolation is ignored inside i18n
• Expecting raw {{ userName }} to show
• Assuming missing translation error for default locale

4. You run ng extract-i18n but the generated translation file is empty. What is the most likely cause?

medium

A. The Angular CLI version is outdated

B. No i18n attributes found in templates

C. The app has no components

D. The translation file path is incorrect

Solution

1. Step 1: Understand what ng extract-i18n does

   This command extracts marked text with i18n attributes from templates into translation files.

2. Step 2: Analyze why the file might be empty

   If no i18n attributes exist, there is nothing to extract, resulting in an empty file.

3. Final Answer:

   No i18n attributes found in templates -> Option B

4. Quick Check:

   Empty extraction file means no i18n markers found [OK]

Hint: Check templates for i18n attributes before extracting [OK]

Common Mistakes:

• Assuming CLI version causes empty file
• Thinking app components absence causes empty file
• Confusing file path issues with extraction content

5. You want to build your Angular app to support English and French using built-in i18n. Which steps are required to serve users in their language?

hard

A. Extract translations, provide French translation file, build app twice with different locales

B. Add i18n attribute, write translations inline, build once

C. Use runtime translation service only, no build changes needed

D. Create separate components for each language manually

Solution

1. Step 1: Extract translations and provide translation files

   Use Angular CLI to extract text marked with i18n and create translation files for English and French.

2. Step 2: Build the app separately for each locale

   Build the app twice, once with English locale and once with French locale, so each build contains the correct translations.

3. Final Answer:

   Extract translations, provide French translation file, build app twice with different locales -> Option A

4. Quick Check:

   Angular i18n requires extraction, translation files, and separate builds [OK]

Hint: Extract, translate, build per locale to support multiple languages [OK]

Common Mistakes:

• Thinking inline translations replace translation files
• Assuming runtime service handles built-in i18n translations
• Trying to create separate components per language manually