settings_migrator.js

const DefaultSettings = {
    "show_system_reset_message": false,
    "resetStyle": 51,
    "reset_font_color": "#FF4500",
    "sound": false,
    "soundId": 3028
};

module.exports = function MigrateSettings(from_ver, to_ver, settings) {
    if (from_ver === undefined) {
        // Migrate legacy config file
        return Object.assign(Object.assign({}, DefaultSettings), settings);
    } else if (from_ver === null) {
        // No config file exists, use default settings
        return DefaultSettings;
    } else {
        // Migrate from older version (using the new system) to latest one
        if (from_ver + 1 < to_ver) {
            // Recursively upgrade in one-version steps
            settings = MigrateSettings(from_ver, from_ver + 1, settings);
            return MigrateSettings(from_ver + 1, to_ver, settings);
        }

        // If we reach this point it's guaranteed that from_ver === to_ver - 1, so we can implement
        // a switch for each version step that upgrades to the next version. This enables us to
        // upgrade from any version to the latest version without additional effort!
        switch (to_ver) {
            case 2:
                delete settings.flashing_notification;
                settings.sound = false;
                break;
            case 3:
                settings.soundId = 3028;
                settings.resetStyle = 51;
        }

        return settings;
    }
};