Angular

Internationalization (I18N) in Angular with Transloco

Published Aug 28, 2020

Updated Feb 16, 2023

7 min read

This article was written over 18 months ago and may contain information that is out of date. Some content may be relevant but please refer to the relevant official documentation or available resources for the latest information.

In this post, I'm going to talk about internationalization and how to implement it in an Angular application with the help of a neat library called Transloco.

What is Internationalization (I18N)?

I think it's best to start by explaining what internationalization (i18n for short - first letter of the word followed by the number of letters until the last letter of the word) is and why it is so important.

Internationalization is the process of adapting a software application to allow it to be easily used in multiple countries. There is a common misconception that this means that all text within an application must have translations for multiple languages; however, full i18n goes beyond just plain text in your application.

In many western countries, red is commonly used to signal danger. However, in some regions throughout the world, red is seen as a positive color.
Likewise, in many western countries, text is read from left to right; however, in some languages text is read from right to left.

Another example of where i18n comes into play is in images. If an image in your application contains text, to fully support i18n, it may be appropriate to generate multiple images each with the correct translations for the languages you support in your application. You would then need to serve the correct image depending on what country the user using your application is located in.

Naomi Meyer gave a brilliant talk on this subject at AngularConnect. You can watch that talk here if you are interested in learning more about. It's worth watching!

What is Transloco?

Transloco is a library developed and maintained by the NgNeat team. It contains a multitude of features and officially supported plugins to help make translating your Angular applications easy, maintainable, scalable and performant. It is actively maintained and it supports:

Lazy loading
Multiple fallbacks
Server-side rendering
Localization (l10n)
Runtime language changing
Multiple languages simultaneously
Pluralization (through an official plugin)

It's very easy to set up and use as we'll see in the next part of this post!

Integrating Transloco into an Angular Application

Now it's time to get our hands into some code! Let's start with a clean slate. I'll assume you have nodejs and npm installed already. If not, I recommend using the LTS version!

Installation

If you don't already have the Angular CLI installed globally, run the following command in your favourite shell:

npm install -g @angular/cli

This will install the Angular CLI globally. Next, we'll create a new app using the Angular CLI:

ng new transloco-test

You'll be given a few prompts. To try out the library, we don't need anything too crazy:

➜ ng new transloco-test
? Would you like to add Angular routing? No
? Which stylesheet format would you like to use? CSS

Now we'll need to navigate into the newly created transloco-test folder: cd transloco-test

From here we can use the ng add command to add Transloco to our application.
Note: By running the ng add Schematic, Transloco will automatically create files in our project to cover the initial set up process!

ng add @ngneat/transloco

After running this command we'll see some prompts from the library for the initial set up. For now, we will stick to the defaults:

? 🌍 Which languages do you need? en, es
? 🚀 Are you working with server side rendering? No

We will also see that some files were created and updated: Ng Add Schematic Output

Let's take a quick look at these files.
tranloco.config.js - stores some basic configuration settings used by some additional Transloco tools.
src/assets/i18n/{en|es}.json - these are the files in which our translations are stored. Usually, one file per language supported. They are set up as key-value pairs, however, Transloco does support nested keys.
src/app/transloco/transloco-root.module.ts - this file sets up the Transloco module, config, transpiler and translation loader.

Let's take a closer look at this file.

@Injectable({ providedIn: "root" })
export class TranslocoHttpLoader implements TranslocoLoader {
  constructor(private http: HttpClient) {}

  getTranslation(lang: string) {
    // We can see here that the file names of our translations are important
    // They must match the available languages in our app
    return this.http.get<Translation>(`/assets/i18n/${lang}.json`);
  }
}

@NgModule({
  exports: [TranslocoModule],
  providers: [
    {
      provide: TRANSLOCO_CONFIG,
      useValue: translocoConfig({
        // These strings of available langs must match our translation file names
        availableLangs: ["en", "es"],
        defaultLang: "en",
        // Remove this option if your application doesn't support changing language in runtime.
        reRenderOnLangChange: true,
        prodMode: environment.production,
      }),
    },
    { provide: TRANSLOCO_LOADER, useClass: TranslocoHttpLoader },
  ],
})
export class TranslocoRootModule {}

This file stores the configuration and the translation loading strategy that Transloco will use to fetch the translations for our app.
It's important to note that the filenames of our translation files must match the array of availableLangs that we support in the app.

Adding Translations to our templates

Transloco provides multiple methods for fetching translations in our templates:

Pipe
Attribute Directive
Structural Directive

Let's look at how to do each in turn.

First, we will set up some translations in our en.json located in our assets/i18n folder:

{
  "title": "Transloco Test",
  "welcomeText": "Hello {{ name }}"
}

Notice that welcomeText contains {{ name }}: this is a dynamic value that we pass into the translation.

We will also up es.json. You can translate this yourself if you want, I'm just going to prefix the translations with ES- to show the differentiation between the translations:

{
  "title": "ES- Transloco Test",
  "welcomeText": "ES- Hello {{ name }}"
}

Open up app.component.html and delete all the content in the file and insert the following:

<div>
  <h1>{{ 'title' | transloco }}</h1>
  <h3>{{ 'welcomeText' | transloco: {name: 'World'} }}</h3>
</div>

Now if you run the app using ng serve you should see the following:
Translated Text

Awesome! Transloco was able to find our keys and successfully fetch the correct translations for it!

We can also use an attribute directive to achieve the same result:

<div>
  <h1 transloco="title"></h1>
  <h3 transloco="welcomeText" [translocoParams]="{name: 'World'}"></h3>
</div>

I personally feel like this approach works well when you aren't providing dynamic values to the translation and are just using transloco="title". With multiple params it could get messy.

The final option for performing translations in the template is to use a structural directive. My favourite method personally.

<div *transloco="let t">
  <h1>{{ t('title') }}</h1>
  <h3>{{ t('welcomeText', {name: 'World'}) }}</h3>
</div>

All three approaches will give the same output; however, there is a performance benefit to using the structural directive approach. It only uses one subscription to update the full template during language changes and change detection cycles.

We can also get translations in your TS files if we need them:

Open app.component.ts and inject TranslocoService into the constructor.


constructor(
    private readonly translocoService: TranslocoService
){}

ngOnInit() {
    // We can then use the service to fetch translations
    const example = this.translocoService.translate('welcomeText', {
      name: 'World',
    });
}

Supporting Runtime Language Change

One of the greatest features of Transloco is that it allows you to change the language of the translations at runtime. And it's super simple to do!

Open up the app.component.ts file and create a new method:

  switchLanguage() {
    if (this.translocoService.getActiveLang() === 'en') {
      this.translocoService.setActiveLang('es');
    } else {
      this.translocoService.setActiveLang('en');
    }
  }

Now, when this method is called the translations will be changed from en to es.

Open app.component.html and add a button to toggle the language:

<div>
  <h1>{{ "title" | transloco }}</h1>
  <h3>{{ "welcomeText" | transloco: { name: "World" } }}</h3>
</div>

<button (click)="switchLanguage()">Switch Language</button>

Now, when we click on the button we should see our translations update in real-time: Language Switching

Pluralization Support

It's fantastic being able to set translations and have them rendered on screen, but what about the following scenario?

{{ numberOfSeconds }} seconds remaining

If numberOfSeconds is 1, that should read 1 second remaining but it won't. It will always render 1 seconds remaining.

That's a problem! However, Transloco has an official plugin that adds MessageFormat support.

The MessageFormat Plugin can be easily added to our app and used to support pluralization and gender in our translations.

Let's see how to add it. First, we need to install two new packages:

npm i messageformat @ngneat/transloco-messageformat

Then we need to initialize it in our TranslocoRootModule, so open transloco/transloco-root.module.ts and add the following to the imports array:

@NgModule({
  imports: [
    TranslocoMessageFormatModule.init()
  ]
  ...
})
export class TranslocoRootModule {}

And voila! Support has been added. But how do we use it?

Let's implement a {{ numOfResults }} search results translation to see it being used.

Open assets/i18n/en.json and add the following key-translation pair:

{
    ...,
    "searchResults": "{numOfResults, plural, =0 {no results found} one {1 search result} other {# search results}}"
}

Now in our app.component.html add the following below the welcome text:

<p>{{ t('searchResults', numOfResults) }}</p>

Finally, in your app.component.ts set a new property called numOfResults:

export class AppComponent {
    numOfResults = 0;

    ...
}

Change the value of numOfResults to see the translation change appropriately!

Final Regards

Hopefully, this article shows how easy it is to implement I18N support into our Angular apps with the help of Transloco! Transloco has so many more features and plugins available to make your i18n experience even nicer.

Two that I'd like to call out are:

Translation Flattening

Transloco supports nested keys:

{
  "aria": {
    "label": "My Translatable A11Y Label"
  }
}

To resolve this, it must loop through each layer of nesting to find the appropriate key. Transloco has a tool available which will flatten the file to:

{
  "aria.label": "My Translatable A11Y Label"
}

Allowing for an O(1) (Big O Notation) lookup. Here's a link to the docs on how to achieve it: https://ngneat.github.io/transloco/docs/tools/optimize

Monorepo Support

Transloco also has a tool to extract translations from libraries within a monorepo, or from npm packages, to allow for more control over where we place our translations, allowing them to be close to the files they are used in. Here is a link to the documentation surrounding the Scoped Library Extractor Tool

This Dot is a consultancy dedicated to guiding companies through their modernization and digital transformation journeys. Specializing in replatforming, modernizing, and launching new initiatives, we stand out by taking true ownership of your engineering projects.

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About the author(s)

Colum Ferry
JavaScript Developer and Enthusiast. Really enjoy working with Angular. Married with 2 amazing kids. Powered by Coffee.
@FerryColum @https://github.com/coly010

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Exploring Angular Forms: A New Alternative with Signals

Exploring Angular Forms: A New Alternative with Signals In the world of Angular, forms are essential for user interaction, whether you're crafting a simple login page or a more complex user profile interface. Angular traditionally offers two primary approaches: template-driven forms and reactive forms. In my previous series on Angular Reactive Forms, I explored how to harness reactive forms' power to manage complex logic, create dynamic forms, and build custom form controls. A new tool for managing reactivity - signals - has been introduced in version 16 of Angular and has been the focus of Angular maintainers ever since, becoming stable with version 17. Signals allow you to handle state changes declaratively, offering an exciting alternative that combines the simplicity of template-driven forms with the robust reactivity of reactive forms. This article will examine how signals can add reactivity to both simple and complex forms in Angular. Recap: Angular Forms Approaches Before diving into the topic of enhancing template-driven forms with signals, let’s quickly recap Angular's traditional forms approaches: 1. Template-Driven Forms: Defined directly in the HTML template using directives like ngModel, these forms are easy to set up and are ideal for simple forms. However, they may not provide the fine-grained control required for more complex scenarios. Here's a minimal example of a template-driven form: ` ` 2. Reactive Forms: Managed programmatically in the component class using Angular's FormGroup, FormControl, and FormArray classes; reactive forms offer granular control over form state and validation. This approach is well-suited for complex forms, as my previous articles on Angular Reactive Forms discussed. And here's a minimal example of a reactive form: ` ` Introducing Signals as a New Way to Handle Form Reactivity With the release of Angular 16, signals have emerged as a new way to manage reactivity. 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Unlike TypeScript, Zod schemas aren't removed on compilation to JavaScript—we still have access to them! If our app receives some data, we can verify that it matches the expected shape by passing it to your Zod schema's parse function. You'll either get back your data in exactly the shape you defined in your schema, or Zod will give you an error to tell you what was wrong. Zod schemas aren't a replacement for TypeScript; rather, they are an excellent complement. Once we've defined our Zod schema, it's simple to derive a TypeScript type from it and to use that type as we normally would. But when we really need to be sure our data conforms to the schema, we can always parse the data with our schema for that extra confidence. Defining Data Schemas Zod schemas are the variables that define our expectations for the shape of our data, validate those expectations, and transform the data if necessary to match our desired shape. It's easy to start with simple schemas, and to add complexity as required. Zod provides different functions that represent data structures and related validation options, which can be combined to create larger schemas. In many cases, you'll probably be building a schema for a data object with properties of some primitive type. For example, here's a schema that would validate a JavaScript object representing an order for a pizza: ` Zod provides a number of primitives for defining schemas that line up with JavaScript primitives: string, number, bigint, boolean, date, symbol, undefined, and null. It also includes primitives void, any, unknown, and never for additional typing information. In addition to basic primitives, Zod can define object, array, and other native data structure schemas, as well as schemas for data structures not natively part of JavaScript like tuple and enum. The documentation contains considerable detail on the available data structures and how to use them. Parsing and Validating Data with Schemas With Zod schemas, you're not only telling your program what data should look like; you're also creating the tools to easily verify that the incoming data matches the schema definitions. This is where Zod really shines, as it greatly simplifies the process of validating data like user inputs or third party API responses. Let's say you're writing a website form to register new users. At a minimum, you'll need to make sure the new user's email address is a valid email address. For a password, we'll ask for something at least 8 characters long and including one letter, one number, and one special character. (Yes, this is not really the best way to write strong passwords; but for the sake of showing off how Zod works, we're going with it.) We'll also ask the user to confirm their password by typing it twice. First, let's create a Zod schema to model these inputs: ` So far, this schema is pretty basic. It's only making sure that whatever the user types as an email is an email, and it's checking that the password is at least 8 characters long. But it is *not* checking if password and confirmPassword match, nor checking for the complexity requirements. Let's enhance our schema to fix that! ` By adding refine with a custom validation function, we have been able to verify that the passwords match. If they don't, parsing will give us an error to let us know that the data was invalid. We can also chain refine functions to add checks for our password complexity rules: ` Here we've chained multiple refine functions. You could alternatively use superRefine, which gives you even more fine grained control. Now that we've built out our schema and added refinements for extra validation, we can parse some user inputs. Let's see two test cases: one that's bound to fail, and one that will succeed. ` There are two main ways we can use our schema to validate our data: parse and safeParse. The main difference is that parse will throw an error if validation fails, while safeParse will return an object with a success property of either true or false, and either a data property with your parsed data or an error property with the details of a ZodError explaining why the parsing failed. In the case of our example data, userInput2 will parse just fine and return the data for you to use. But userInput1 will create a ZodError listing all of the ways it has failed validation. ` ` We can use these error messages to communicate to the user how they need to fix their form inputs if validation fails. Each error in the list describes the validation failure and gives us a human readable message to go with it. You'll notice that the validation errors for checking for a valid email and for checking password length have a lot of details, but we've got three items at the end of the error list that don't really tell us anything useful: just a custom error of Invalid input. The first is from our refine checking if the passwords match, and the second two are from our refine functions checking for password complexity (numbers and special characters). Let's modify our refine functions so that these errors are useful! We'll add our own error parameters to customize the message we get back and the path to the data that failed validation. ` Now, our error messages from failures in refine are informative! You can figure out which form fields aren't validating from the path, and then display the messages next to form fields to let the user know how to remedy the error. ` By giving our refine checks a custom path and message, we can make better use of the returned errors. In this case, we can highlight specific problem form fields for the user and give them the message about what is wrong. Integrating with TypeScript Integrating Zod with TypeScript is very easy. Using z.infer<typeof YourSchema> will allow you to avoid writing extra TypeScript types that merely reflect the intent of your Zod schemas. You can create a type from any Zod schema like so: ` Using a TypeScript type derived from a Zod schema does *not* give you any extra level of data validation at the type level beyond what TypeScript is capable of. If you create a type from z.string.min(3).max(20), the TypeScript type will still just be string. And when compiled to JavaScript, even that will be gone! That's why you still need to use parse/safeParse on incoming data to validate it before proceeding as if it really does match your requirements. A common pattern with inferring types from Zod schemas is to use the same name for both. Because the schema is a variable, there's no name conflict if the type uses the same name. However, I find that this can lead to confusing situations when trying to import one or the other—my personal preference is to name the Zod schema with Schema at the end to make it clear which is which. Conclusion Zod is an excellent tool for easily and confidently asserting that the data you're working with is exactly the sort of data you were expecting. It gives us the ability to assert at runtime that we've got what we wanted, and allows us to then craft strategies to handle what happens if that data is wrong. Combined with the ability to infer TypeScript types from Zod schemas, it lets us write and run more reliable code with greater confidence....

Nov 15, 2024

7 mins

JavaScriptZod

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