aurelia-i18next

This plugin is part of the Aurelia platform. It sets up a wrapper for the i18next library.

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Table of Contents generated with DocToc

How to install this plugin?
How to use this plugin
CLI Integration
Running the unit tests

How to install this plugin?

In your project install the plugin via jspm with following command

jspm install aurelia-i18next=github:zewa666/aurelia-i18next

Make sure you use manual bootstrapping. In order to do so open your index.html and locate the element with the attribute aurelia-app. Change it to look like this:

<body aurelia-app="main">
...

Create folder locale in your projects root
For each locale create a new folder with it's name (e.g. en, de, ...)
In those subfolders create a file named translation.json which contains your language specific translations. Below you can find a sample en-EN translation file. The full potential of i18next is achieved through a specific translation-file schema. Consult the i18next docs to find out more about it.

{
  "score": "Score: __score__",
  "lives": "__count__ life remaining",
  "lives_plural": "__count__ lives remaining",
  "lives_indefinite": "a life remaining",
  "lives_plural_indefinite": "some lives remaining",
  "friend": "A friend",
  "friend_male": "A boyfriend",
  "friend_female": "A girlfriend"
}

6.. Create (if you haven't already) a file main.js in your src folder with following content:

  import {I18N} from 'aurelia-i18next';

  export function configure(aurelia) {
    aurelia.use
      .standardConfiguration()
      .developmentLogging()
      .plugin('aurelia-i18next', (instance) => {
        // adapt options to your needs (see http://i18next.com/pages/doc_init.html)
        instance.setup({
          resGetPath : 'locale/__lng__/__ns__.json',
          lng : 'de',
          attributes : ['t','i18n'],
          getAsync : true,
          sendMissing : false,
          fallbackLng : 'en',
          debug : false
        });
      });

    aurelia.start().then(a => a.setRoot());
  }

How to use this plugin

i18next translations work by setting up an active locale, which you've setup above in the init phase with the property lng.

Setting the active locale

In order to change the active language you'd have to call the function setLocale(localeName) via code.

import {I18N} from 'aurelia-i18next';

export class MyDemoVM {
	static inject = [I18N];
	constructor(i18n) {
	  this.i18n = i18n;
		this.i18n
		    .setLocale('de-DE')
		    .then( () => {
			// locale is loaded
		});
	}
	...
}

Getting the active locale

To get the active locale you'd go with getLocale():

import {I18N} from 'aurelia-i18next';

export class MyDemoVM {
	static inject = [I18N];
	constructor(i18n) {
	   this.i18n = i18n;
		 console.log(this.i18n.getLocale());
	}
	...
}

Translating via code

Translating stuff via code works by using the method tr. You pass in the key as first parameter, followed by the optional second parameter options to specify in detail how the translations should be performed. Please consult the i18next docs for a detailed list of those:

import {I18N} from 'aurelia-i18next';

export class MyDemoVM {
	static inject = [I18N];
	constructor(i18n) {
	   this.i18n = i18n;
		 console.log(this.i18n.tr('mykey'));
	}
	...
}

Translating via html attributes

Translation in html can be done alternatively using attributes. By default the plugin is configured to use the t and i18n attributes. This can be configured during the plugin registration using the attributes property.

...
instance.setup({
	...
	attributes : ['t','i18n'],
	...
});
...

Any element in your views that has one of those attributes, will be translated when the locale is changed.

<span t="title">Title</span>

The plugin will use the title as the key when translating that element. Other attributes, specified in the attributes option, may be used as well.

<span i18n="home.title">Title</span>

Notice in the above example that the key was set to home.title. This will make the plugin look for a translation with nested objects in your translation json, ie:

{
  "home": {
    "title": "Title",
  }
}

Use updateTranslation() to update all translations within the children of the element that is passed to it. The following example shows how a view model can be configured to update it's contents when the view is attached and every time a locale is changed.

import {I18N} from 'aurelia-i18next';
import {EventAggregator} from 'aurelia-event-aggregator';

export class MyDemoVM {
  static inject = [I18N,Element,EventAggregator];
  constructor(i18n,element,ea) {
    this.i18n = i18n;
    this.element = element;
	   
	  ea.subscribe('i18n:locale:changed', payload => {
	    this.i18n.updateTranslations(this.element);
	  });
  }
  
  attached(){
    this.i18n.updateTranslations(this.element);
  }
}

Specifying attributes

By default the plugin will set the textContent property of an element.

//translation
{
  "title": "Title <b>bold</b>"
}

//markup
<span t="title">Title</span>

So in above example the html tags will be escaped and the output will be <b>bold</b>. To allow html-markup to be used, the [html] attribute needs to be added before the translation key.

<span t="[html]title">Title</span>

This will set the innerHTML of the element instead of the textContent property, so html-markup won't be escaped. There are 4 special attributes including the shown [html]:

[text]: Sets the textContent property (default)
[html]: Sets the innerHTML property
[append]: appends the translation to the current content already present in the element (allows html).
[prepend]: prepends the translation to the current content already present in the element (allows html).

Any other values will be used as actual attributes on the element. The following example will not change the content of the element, but will set its alt attribute to the translated value of title when the locale changes.

<span t="[alt]title">Title</span>

Specifying multiple attributes

Multiple attributes can be specified by separating them with a semicolon.

<span t="[html]title;[class]title-class">Title</span>

When the locale changes it will set the innerHTML to the translated value of title due to the [html] attribute and the class property to the translated value of title-class.

Using nested and combined translations

In order to combine two or more translations, just include them with the $t(yourkey) markup

<span t="$t(title) $t(subtitle)">Title subtitle</span>

Nested keys may also be referenced and will be properly translated:

{
  "translation": {
    "title": "Title",
    "nested_referencing": 'The $t(title) is the header',
    ...
  }
}

<span t="nested_referencing">Nested text</span>

Translating images

Images can be translated as well, for when a different image needs to be displayed in another language.

<img t="home.image" />

The plugin will automatically change the src attribute of the image when the locale changes.

You may specify a default value for images as well. In order to do so just define an attribute called data-src with the default value.

<img data-src="path/to/image.jpg" t="home.image" />

This will be picked up by the CLI when translations are extracted from the source files. (see the section on CLI Integration)

Translating with the TValueConverter

In order to do translations in a more declarative way from within your HTML markup you can use a custom ValueConverter named t. It takes exactly the same options as the code translation method tr but of course provides the key automatically.

You will find below a few examples of the available i18next features

<template>
  <section>
    <div class="row">
      <div class="col-md-3">
        <h3>ValueConverter Examples</h3>
        <ul class="list-group">
          <li class="list-group-item">
            Translation with Variables: <br />
            ${ 'score' | t: {'score': userScore}}
          </li>

          <li class="list-group-item">
            Translation singular: <br />
            ${ 'lives' | t: { 'count': 1 } }
          </li>

          <li class="list-group-item">
            Translation plural: <br />
            ${ 'lives' | t: { 'count': 2 } }
          </li>

          <li class="list-group-item">
            Translation singular indefinite: <br />
            ${ 'lives' | t: { 'count': 1, indefinite_article: true  } }
          </li>

          <li class="list-group-item">
            Translation plural indefinite: <br />
            ${ 'lives' | t: { 'count': 2, indefinite_article: true } }
          </li>

          <li class="list-group-item">
            Translation without/with context: <br />
            ${ 'friend' | t } <br />
            ${ 'friend' | t: { context: 'male' } } <br />
            ${ 'friend' | t: { context: 'female' } }
          </li>
        </ul>
      </div>
    </div>
  </section>
</template>

Complex objects for variables

In some cases it might be useful to define variables via complex objects. Let's take a look at below example. It shows a validation message to hint the user that a given field should be in range of min and max. Now we could easily pass min and max as separate variables but on the other hand that involves more work you'd have to do manually if the source is a object.

var resources = {
  en: {
    translation: {
      "complex": '__field__ should be between __threshold.min__ and __threshold.max__'
    }
  }
};

So in order to avoid that you may simply pass in the object as a whole and the library will pickup all the necessary information and create the proper options object. You can also mix and match it with simple variables.

var options = {
  'threshold': {
    'min': 1,
    'max': 10
  },
  'field': 'Age'
};

i18n.tr('complex', options);
// --> Age should be between 1 and 10

Formatting numbers via code

For displaying numbers in different formats, this plugin makes use of the Internationalization API NumberFormat. It leverages the same locales used for the translation methods mentioned in the install process of the plugin.

The API provides access to the Intl NumberFormat with the method NumberFormat. This function takes the an options object representing the formatting options as the first and the locale as the second parameter.

Below is an example how to access the NumberFormat via code:

import {I18N} from 'aurelia-i18next';

export class MyDemoVM {
  static inject = [I18N];
	constructor(i18n) {
	  this.i18n = i18n;
	    
	  // create a NumberFormat with German locale
    var nf = this.i18n.nf(undefined, 'de');
	  var result = nf.format(123456.123);
		
	  console.log(result);
	  // output => 123.456,123

		
	  // create a NumberFormat with currency options
	  var nf = this.i18n.NumberFormat({ style: 'currency', currency: 'EUR' }, 'de');

	  var result = nf.format(123456.123);
		
	  console.log(result);
	  // output => 123.456,123 €  	  
	}
	...
}

Formatting numbers with NfValueConverter

A more declarative way is to use the nf ValueConverter from within your HTML markup. It essentially works the same way as the code version. Take a look at the following example:

<div class="col-md-3">
  <h3>ValueConverter Number Examples</h3>
  <ul class="list-group">
    <li class="list-group-item">
      Numberformat with default locale/format:
      ${ 1234567.890 | nf : undefined : selectedLocale}
    </li>
    <li class="list-group-item">
      Numberformat with different locale default format:
      ${ 1234567.890 | nf : undefined : 'de'}
    </li>
    <li class="list-group-item">
      Numberformat with different locale/format:
      ${ 1234567.890 | nf : { style: 'currency', currency: 'EUR' } : 'de'}
    </li>
  </ul>
</div>

Note that if you provide the active locale as a bound VM property, the ValueConverter will be re-evaluated as soon as the property value changes, resulting in automatic re-formatting of your number.

Formatting dates via code

The Intl. API provides means to format DateTimes as well. Use the method df to access that feature with the same arguments used for NumberFormat Below you'll find an example how to use those via code:

import {I18N} from 'aurelia-i18next';

export class MyDemoVM {
  static inject = [I18N];
	constructor(i18n) {
	  this.i18n = i18n;
	    
	  // create a DateTimeFormat with German locale
    var df = this.i18n.df(undefined, 'de');
	  var result = df.format(new Date(2000, 0, 1, 0,0,1))
		
	  console.log(result);
	  // output => 1.1.2000

		
	  // create a DateTime with time and 2-digit display
	  var options = {
      year: 'numeric', month: '2-digit', day: '2-digit',
      hour: '2-digit', minute: '2-digit', second: '2-digit',
      hour12: false
    };
	  var df = this.i18n.df(options, 'de');

	  var result = df.format(new Date(2000, 0, 1, 0,0,1));
		
	  console.log(result);
	  // output => 01.01.2000 00:00:01  	  
	}
	...
}

Remember that if you pass in undefined for the options parameter you'll get the default formatting options

Formatting dates with DfValueConverter

A more declarative way is to use the df ValueConverter from within your HTML markup. It essentially works the same way as the code version. Take a look at the following example, which defines a VM property myDate:

<div class="col-md-3">
  <h3>ValueConverter Date Examples</h3>
  <ul class="list-group">
    <li class="list-group-item">
      DateFormat with default locale/format:
      ${ myDate | df : undefined : selectedLocale}
    </li>
    <li class="list-group-item">
      DateFormat with different locale default format:
      ${ myDate | df : undefined : 'de'}
    </li>
    <li class="list-group-item">
      DateFormat with different locale/format:
      ${ myDate | df : { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric' } : 'de'}
    </li>
  </ul>
</div>

Rendering relative time

In order to create a representation of relative time like x days ago or in x days you can leverage the Service relativeTime. This exposes a method getRelativeTime which accepts a valid JS date. To use it via code get hold of the service via injection and call the method as needed:

import {RelativeTime} from 'aurelia-i18next';

export class MyDemoVM {
  static inject = [I18N];
	constructor(relativeTime) {
	  this.rt = relativeTime;
	    
	  var myDate = new Date();
    myDate.setHours(myDate.getHours() - 2);
		
	  console.log(result);
	  // output => 2 hours ago  	  
	}
	...
}

This is also tied in to the currentLocale of the library so changing that one will also translate relative time messages. Take a look at the file src/defaultTranslations/relative.time.js for available translations. If you're missing yours I welcome you to provide a PR so everybody can benefit from it.

A more declarative approach is to use the RtValueConverter directly in your HTML markup. It's not taking any additional parameters so just drop it in and you're good to go:

<div class="col-md-3">
  <h3>ValueConverter Relative Time Examples</h3>
  <ul class="list-group">
    <li class="list-group-item">
      2 hours ago:
      ${ myDate | rt }
    </li>
  </ul>
</div>

CLI Integration

There will be a command line tool that can create translation.json files for you by extracting the values from the html and javascript files. (coming soon)

Running the unit tests

In order to properly run the unit tests please install the defined jspm devDependencies by running the following command:

jspm install --dev

To start the tests just run:

karma start

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