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JavaScript

Native JavaScript Multilanguage Templating

In the project I’m currently working on, I faced the “problem” to integrate multilanguage support, but due to the fact that the new app should be written in vanilla JS, without any plugins, libraries or other dependencies, I had to develop my own localization layer. In this article I want to show you my approach on this…

My solution is based on a template system that I implemented into my project at an earlier stage. If you are interested in how this works, I recommend you read my article Utilize a repository of reusable ES6 template literals.

Let’s start with the standard scaffold of an HTML5 app, extended with some style‘s, an initialization script and a lonely main element, we want to fill with some localized content:

index.html
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<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <meta http-equiv="language" content="en">

        <title>Native JavaScript Multilanguage Templating</title>

        <style>
            body { padding: 2rem; }
            main { text-align: center; }
        </style>

        <script type="module">
            import { App } from './app.js';
            window.app = new App(); 
            app.init();
        </script>

    </head>

    <body>
        <main></main>
    </body>

</html>

The script points to the following ES6 module class in the file app.js:

app.js
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class App {

  constructor() { 
    // do something when the class is instantiated
  }

  init() {
    // do something to initialize the app
  }
}
export { App };

Nothing uncommon so far, if you are familiar with ES6 classes and imports/exports.

Now let’s create a localizations.js file, to store the needed localized strings in all wanted languages. Every language will have its own branch in a Localizations object, represented by its two-letter ISO-639-1 language code. All translations are accessible via an unique english key word:

localizations.js
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export function Localizations() {
    return {
        "EN": {
            "helloWorld": "Hello World"
        },
        "DE": {
            "helloWorld": "Hallo Welt"
        },
        "ES": {
            "helloWorld": "Hola, mundo"
        },
        "FR": {
            "helloWorld": "Bonjour le monde"
        },
        "RU": {
            "helloWorld": "Здравствуйте, мир"
        },
        "JP": {
            "helloWorld": "ハローワールド"
        }
    }
}

As we import the localizations.js in our app.js, we can initialize the localizations in the constructor of the app class with the language code of the users browser:

app.js
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import { Localizations } from './localizations.js';

class App {

  constructor() { 
    
    // Get browser language
    this.langCode = 
      window.navigator.language.split("-")[0].toUpperCase();

    // Init localization to access via 'app.localization' globally
    this.localization = Localizations()[this.langCode];

  }

  ...

app.localization now holds the key/value list of the current language.

Now we implement the templating class, as described in Utilize a repository of reusable ES6 template literals and define a first template called helloWorld …

templates.js
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class Templates {

    helloWorld(data) {
        return this.fillTemplate(`
            <h1>${app.localization.helloWorld}</h1>
        `, data);
    }

    fillTemplate(templateString, templateVars){
        var func = new Function(...Object.keys(templateVars),  
          "return `" + templateString + "`;");
        return func(...Object.values(templateVars));
    }
}
export { Templates };

The inner text of the h1 element in the helloWorld template refers to the globally available variable app.localization, we initialized in the last step, and points to the translation helloWorld.

In app.js we import the templates.js and implement some code in the init method, to get the template and bring it to the DOM:

app.js
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import { Localizations } from './localizations.js';
import { Templates } from './templates.js';

class App {

  ...

  init() { 

    // Get "Hello World" H1 element in current language
    let helloWorld = app.templates.helloWorld({});

    //Insert H1 element into MAIN element
    document.querySelector("main")
      .insertAdjacentHTML("beforeend", helloWorld);

  }

This is it …

In the following Github repository you will find a solution based on this example, extented with a language selector, cookie support and some helper methods to keep the code nice and clean:

https://github.com/kristofzerbe/Native-JavaScript-Multilanguage-Templating

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