translations.js

var localizedTranslations = {};
var translationBase = {};
var appTranslations = {};


function loadTranslationLanguage(language) {
    script = document.createElement("script");
    script.src = "../translations/" + language + ".js";
    document.head.appendChild(script);
}

function getUserLocale() {
    // example to match from the WebView of the app:
    // "Mozilla/5.0 (Linux; U; Android 2.3.5; de-de; GT-I9001 Build/GINGERBREAD) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1 | language: en"
    var languageMatch = navigator.userAgent.match(/\|\s*language:\s*(\S+)$/);
    var locale = languageMatch == null ? navigator.language : languageMatch[1];
    return locale;
}

function getUserLanguage() {
    return getUserLocale().split("-")[0];
}

function getUserCountry() {
    return getUserLocale().split("-")[1];
}

var language = getUserLanguage();
log.log("The browser language is " + language);
var defaultLanguage = "en";

var define = function (newTranslations) {
    log.log("loaded translations for " + defaultLanguage);
    translationBase = newTranslations;
    //log.log("base translations", newTranslations);
    if (defaultLanguage == language) {
        localizedTranslations = translationBase;
        _notifyThatTheTranslationsAreLoaded();
    } else {
        define = function(newTranslations) {
            localizedTranslations = newTranslations;
            //log.log(language + " translations", newTranslations);
            log.log("loaded translations for " + language);
            _notifyThatTheTranslationsAreLoaded();
        }
        loadTranslationLanguage(language);
    }
}

loadTranslationLanguage(defaultLanguage);

function translate(key) {
    var lookupChain = [
        [appTranslations, null],
        [localizedTranslations, "key " + key + " is not translated to " + language],
        [translationBase, "ERROR: key " + key + " is not found in the " + defaultLanguage + " translations. It should be there. Make sure it is not misspelled."],
    ];
    for (var i = 0; i < lookupChain.length; i++) {
        translations = lookupChain[i][0];
        var translation = translations[key];
        if (translation != undefined) {
            return translation;
        }
        var errorMessage = lookupChain[i][1];
        if (errorMessage) {
            log.log(errorMessage);
        }
    }
    return key;
}

function _notifyThatTheTranslationsAreLoaded0() {
    log.log("All translations are loaded.");
    clearTimeout(translationsLoadingTimeout); // see https://stackoverflow.com/a/2578642
    translationsLoadingTimeout = null; // so we can check in the console
}
var toNotifyAboutLoad = [_notifyThatTheTranslationsAreLoaded0];
function _notifyThatTheTranslationsAreLoaded() {
    toNotifyAboutLoad.forEach(function (callback) {
        callback();
    });
    toNotifyAboutLoad = [];
}

function onNotifyThatTheTranslationsAreLoaded(callback) {
    if (toNotifyAboutLoad.length == 0) {
        // after loading took place
        callback();
    } else {
        // before loading took place
        toNotifyAboutLoad.push(callback);
    }
}

// notify about translations even if they do not exist.
var translationsLoadingTimeout = setTimeout(function() {
        _notifyThatTheTranslationsAreLoaded();
        log.log("Loading translations timed out.");
    }, 1000);

function loadJSONTranslations() {
    getAppTranslations(function (translations){
        appTranslations = translations;
    });
}

window.addEventListener("load", loadJSONTranslations);