cox-svelte

Cox is an modern fully-typed Typescript library to handle internationalisation.

Cox-svelte is an adapter of the Cox library for the front-end framework Svelte.

Comparing to standard internationalisation libraries, it has the following features:

• type safe. Using Typescript, Cox ensures that you have no missing key for any locale at any moment. Even when dealing with many languages, you can deploy in production with confidence: you'll never make a mistake again.
• no string key. Standard internationalisation libraries use this kind of syntax to get a content value: $t('unsafe.path.to.my.key'). It is error-prone, very annoying to write and not typed. With Cox, you'll write something like: $content.safe.path.to.my.key, with auto-completion and the right typing.
• use functions instead of templates. There are so many languages, dealing with plural, feminine/masculine, and other stuff is very complex. It's actually so complex there is no simple and magic template language that can do it all. Cox is developper-oriented and instead of implementing a complex template language, it lets the developper decide how to to deal with edge cases. The use of the natively embedded Intl library is highly encouraged along Cox.
• not one huge translation file. Instead of having one huge en.json file for every language, Cox promotes the use of multiples smaller translation files. Typically, you would apply content per-component instead of globally. This improves drastically the developper experience.

When to use and when to not use

Cox is a perfect choice when you develop an application with few languages (maximum 4-5 languages).

I you need to develop a product that will be translated a lot of languages, Cox is not recommended. For these use cases, we advice to use a software with an integrated graphical user interface like Weblate.

Usage

First, let's create a configuration file that describes all the languages we will implement.

/* src/locales.ts */
import { defineLocales } from "cox-svelte"

/**
 * We want to implement two languages: english and french.
 * We also indicate that english is the default language.
 */
export const { defineContent, currentLocale } = defineLocales<"en" | "fr">("en")

Then let's define a content file. A content file can contains anything, as long as it contains the same type of data for every locale to implement.

For that, we use the defineContent function that has just been returned:

/* src/content.ts */
import { defineContent } from "./locales"

export const content = defineContent({
  en: {
    sayHelloToWorld: `Hello world!`,
    sayHelloTo: (helloTo: string) => `Hello ${helloTo}!`
  },
  fr: {
    sayHelloToWorld: `Bonjour le monde !`,
    sayHelloTo: (helloTo: string) => `Bonjour ${helloTo} !`
  },
})

Great, now we can use our newly defined content in our svelte components:

<!-- src/component.svelte -->
<script lang="ts">
  import { content } from './content'
</script>

<p>
  { $content.sayHelloToWorld }
</p>

<p>
  { $content.sayHelloTo('magnificent you') }
</p>

Changing current locale

currentLocale is a writable store so it is very easy to change it programmatically:

import { currentLocale } from "./locales"

currentLocale.set("fr")

Alternatively if you are inside a .svelte file you can use the store syntax:

$currentLocale = "fr"

Thanks to the magic of stores, this will automatically update all content data in the entire application.

Note on architecture

Cox promotes the use of one content file per component. This is ideal for codebases that will scale. As a developer, you won't get lost with one humongous json translation file.

Not all components should have their respective content file though. For example, if you follow the atomic design methodology:

• atoms and molecules should not be related to a content file,
• organisms and templates can be related to a content file,
• pages should not be related to a content file - as they import templates and organisms that have this responsibility.