Multilingual translation of JavaScript (Cordova, Web) applications

Overview

You can use the Persistent Mobile Foundation framework to add multilingual translation in JavaScript (Cordova, Web) applications into other languages.
Items that can be translated are application strings and system messages.

Jump to:

• Translating application strings
• Translating system messages
• Multilanguage translation
• Detecting the device locale and language
• Sample application

Translating application strings

Strings that are destined to be translated are stored in a JSON object called “Messages”.

• In Cordova applications that use the PMF SDK, you can find it in the index.js file of the Cordova application: [cordova-project-root-directory]/www/js/index.js.
• In Web applications, you need to add it.

JSON object structure example

var Messages = {
    headerText: "Default header",
    actionsLabel: "Default action label",
    sampleText: "Default sample text",
};

Strings stored in the Messages JSON object can be referenced in two ways in the application logic:

As a JavaScript object property:

Messages.headerText

As an ID of an HTML element with class="translate":

<h1 id="headerText" class="translate"></h1>

Translating system messages

It is also possible to translate the system messages that the application displays, for example “Internet connection is not available” or “Invalid username or password”. System messages are stored in the WL.ClientMessages object.

Note: Override system messages at a global JavaScript level because some parts of the code are executed only after the application has successfully initialized.

Web applications

You can find a full list of system messages in the messages.json file, located in the [project root folder]\node_modules\ibm-mfp-web-sdk\lib\messages\ folder.

Cordova applications

You can find a full list of system messages in the messages.json file, located inside the generated project.

• Android: [Cordova-project]\platforms\android\assets\www\plugins\cordova-plugin-mfp\worklight\messages
• iOS: [Cordova-project]\platforms\[ios]\www\plugins\cordova-plugin-mfp\worklight\messages

To translate a system message, override it in the application code.

WL.ClienMessages.loading = "Application HelloWorld is loading... please wait.";

Multilanguage translation

Using JavaScript, you can implement multilanguage translation for your application.
The below steps explain the implementation of this tutorial’s sample application.

1. Set up the default application strings in the index.js file.

   var Messages = {
        headerText: "Default header",
        actionsLabel: "Default action label",
        sampleText: "Default sample text",
        englishLanguage: "English",
        frenchLanguage: "French",
        russianLanguage: "Russian",
        hebrewLanguage: "Hebrew"
   };
   

2. Override specific strings when required.

   function setFrench(){
        Messages.headerText = "Traduction";
        Messages.actionsLabel = "Sélectionnez une langue:";
        Messages.sampleText = "Ceci est un exemple de texte en français.";
   }
   

3. Update the GUI components with the new strings. You can perform more tasks, such as setting the text direction for right-to-left languages such as Hebrew or Arabic. Each time that an element is updated, it is updated with different strings according to the active language.

   function languageChanged(lang) {
        if (typeof(lang)!="string") 
            lang = $("#languages").val();
           
        switch (lang) {
            case "english":
                setEnglish();
                break;
            case "french":
                setFrench();
                break;
            case "russian":
                setRussian();
                break;
            case "hebrew":
                setHebrew();
                break;
        }
                  
        if ($("#languages").val()=="hebrew")
            $("#wrapper").css({direction: 'rtl'});
        else
            $("#wrapper").css({direction: 'ltr'});
         
        $("#sampleText").html(Messages.sampleText);
        $("#headerText").html(Messages.headerText);
        $("#actionsLabel").html(Messages.actionsLabel);
   }
   

Detecting the device locale and language

To detect the language used by the device or browser:

Web applications

Detect the browser language using navigator.language or any number of available frameworks and solutins.

Cordova applications

Detect the locale and the language of the device using the Cordova’s globalization plug-in: cordova-plugin-globalization.
The globalization plug-in is auto-installed when adding a platform to the Cordova application.

Use the navigator.globalization.getLocaleName and navigator.globalization.getPreferredLanguage functions to detect the locale and language respectively.

navigator.globalization.getLocaleName(
	function (localeValue) {
		WL.Logger.debug(">> Detected locale: " + localeValue);
		
        ...
        ...
        ...
	},
	function() {
		WL.Logger.debug(">> Unable to detect locale.");
	}
);

navigator.globalization.getPreferredLanguage(
	function (langValue) {
		lang = langValue.value;
		WL.Logger.debug(">> Detected language: " + lang);
	},
	function() {
		WL.Logger.debug(">> Unable to detect language.");
	}
);

The result can then be seen in the device log, for example from Android Studio’s LogCat:

Sample application

Click to download the Cordova project.

Sample usage

Follow the sample’s README.md file for instructions.

Tip: you can inspect Android’s LogCat from Android Studio’s LogCat console while the application is running.