Connect-assetmanager question

app.js

require('./bootstrap/bootstrap');

const express = require('express');
const auth    = require('connect-auth');
const config  = require('./config');
const ConnectCouchDB = require('connect-couchdb')(express);
const assetManager = require('connect-assetmanager');
const assetHandler = require('connect-assetmanager-handlers');

const port    = config.keys.port;

const session = {
  secret: config.keys.sessionSecret,
  cookie: { maxAge: 600000 },
  store: new ConnectCouchDB(config.keys.couchDbSessionStoreConfig)
};

const authPlugins = auth.Facebook({
    appId: config.keys.fbId,
    appSecret: config.keys.fbSecret,
    scope: "email",
    callback: config.keys.fbCallbackAddress
});

var server = express.createServer(express.logger( ':method :url :status - :response-time ms' ),
                                  express.responseTime(),
                                  express.cookieParser(),
                                  express.session( session ),
                                  auth( authPlugins ),
                                  express.bodyParser(),
                                  express.router( config.routes ),
                                  express.favicon(),
                                  express.static( __dirname + '/../public' ),
                                  express.errorHandler({ showStack: true, showMessage: true, dumpExceptions: true })
                                );

server.set('views', __dirname + '/views');
server.set('view engine', 'jade');
server.set('view options', { layout: false });


var root = __dirname + '/public';

var assetManagerGroups = {
    'js': {
        'route': /\/static\/javascript\/[0-9]+\/.*\.js/
        , 'path': './public/javascript/'
        , 'dataType': 'javascript'
        , 'files': [
             '*'
        ]
    }, 'css': {
        'route': /\/static\/css\/[0-9]+\/.*\.css/
        , 'path': './public/css/'
        , 'dataType': 'css'
        , 'files': [
             '*'
        ]
        , 'preManipulate': {
            // Regexp to match user-agents including MSIE.
            'MSIE': [
                assetHandler.yuiCssOptimize
                , assetHandler.fixVendorPrefixes
                , assetHandler.fixGradients
                , assetHandler.stripDataUrlsPrefix
            ],
            // Matches all (regex start line)
            '^': [
                assetHandler.yuiCssOptimize
                , assetHandler.fixVendorPrefixes
                , assetHandler.fixGradients
                , assetHandler.replaceImageRefToBase64(root)
            ]
        }
    }
};

var assetsManagerMiddleware = assetManager(assetManagerGroups);
server.use('/'
    , assetsManagerMiddleware
    , express.static(root)
);

server.listen(port);
console.log("server listening at http://localhost:" + port);