localization.js

(function() {
    var locale;
    var messages = {};


    /* Utility functions: */

    /**
     * Replace variables used in the message by appropriate values.
     *
     * @method applyReplacements
     * @static
     * @param {String} message      Input message.
     * @param {Object} replacements Associative array: { variableName: "replacement", ... }
     * @return {String} The input message with all replacements applied.
     */
    var applyReplacements = function (message, replacements) {
        for (var replacementName in replacements) {
            var replacement = String(replacements[replacementName]);

            // 'welcome' => 'Welcome, :name' => 'Welcome, dayle'
            message = message.replace(
                new RegExp(':' + replacementName, 'g'),
                replacement
            );
            // 'welcome' => 'Welcome, :NAME' => 'Welcome, DAYLE'
            message = message.replace(
                new RegExp(':' + replacementName.toUpperCase(), 'g'),
                replacement.toUpperCase()
            );
            // 'welcome' => 'Welcome, :Name' => 'Welcome, Dayle'
            message = message.replace(
                new RegExp(':' + (replacementName.charAt(0).toUpperCase() + replacementName.substr(1)), 'g'),
                replacement.charAt(0).toUpperCase() + replacement.substr(1)
            );
        }

        return message;
    };

    var isEmpty = function (obj) {
        for(var prop in obj) {
            if(obj.hasOwnProperty(prop))
                return false;
        }

        return true;
    };


    /* Lang: */

    /**
     * Lang class. Works similar to the Laravel Lang object.
     * @class Lang
     */

    var Lang = {

        /**
         * Translate a message.
         *
         * @method get
         * @static
         * @param {String} messageKey       The message key (message identifier).
         * @param {Object} [replacements]   Associative array: { variableName: "replacement", ... }
         * @return {String} Translated message.
         */
        get : function(messageKey, replacements, forceLocale) {
            var uselocale = locale;
            if (forceLocale) {
                uselocale = forceLocale;
            }
            if (typeof messages[uselocale][messageKey] == "undefined") {
                /* like Lang::get(), if messageKey is the name of a lang file, return it as an array */
                var result = {};
                for (var prop in messages[uselocale]) {
                    if (prop.indexOf(messageKey + '.') > -1) {
                        result[prop] = messages[uselocale][prop];
                    }
                };
                if (!isEmpty(result)) {
                    return result;
                }
                /* if there is nothing to return, return messageKey */
                return messageKey;
            }

            var message = messages[uselocale][messageKey];

            if (replacements) {
                message = applyReplacements(message, replacements);
            }

            return message;
        },

        /**
         * Returns whether the given message is defined or not.
         *
         * @method has
         * @static
         * @param {String} messageKey   Message key.
         * @return {Boolean} True if the given message exists.
         */
        has : function(messageKey) {
            return typeof messages[locale][messageKey] != "undefined";
        },

        /**
         * Choose one of multiple message versions, based on
         * pluralization rules. Only English pluralization
         * supported for now. If `count` is one then the first
         * version of the message is retuned, otherwise the
         * second version.
         *
         * @method choice
         * @static
         * @param {String} messageKey       Message key.
         * @param {Integer} count           Subject count for pluralization.
         * @param {Object} [replacements]   Associative array: { variableName: "replacement", ... }
         * @return {String} Translated message.
         */
        choice : function(messageKey, count, replacements) {
            if (typeof messages[locale][messageKey] == "undefined") {
                return messageKey;
            }

            var message;
            var messageSplitted = messages[locale][messageKey].split('|');

            if (count == 1) {
                message = messageSplitted[0];
            } else {
                message = messageSplitted[1];
            }

            if (replacements) {
                message = applyReplacements(message, replacements);
            }

            return message;
        },

        /**
         * Sets the current locale. Normally only used once
         * during initialization. The value comes from the backend.
         *
         * @method setLocale
         * @static
         * @param {String} localeId The locale returned by Laravel's Lang::locale().
         * @throws {Error} An error is thrown if messages[localeId] is not defined.
         */
        setLocale : function(localeId) {
            locale = localeId;

            if (!messages[localeId]) {
                throw new Error(
                    'No messages defined for locale: "' + localeId + '". ' +
                    'Did you forget to enable it in the configuration?'
                );
            }
        },

        /**
         * Returns the current locale.
         *
         * @method locale
         * @static
         * @return {String} The current locale.
         */
        locale : function() {
            return locale;
        },

        /**
         * Used to initialize the message catalog. You may use this
         * method to add further messages on runtime if necessary.
         *
         * @method addMessages
         * @static
         * @param {Object} _messages  An associative array: { messageKey: "message", ... }
         */
        addMessages : function(_messages) {
            for (var key in _messages) {
                messages[key] = _messages[key];
            }
        }
    };


    /* Export: */

    this.Lang   = Lang;
    this.trans  = Lang.get;
    this.transChoice = Lang.choice;
})();