Exploring Express use order

index.js

var express = require('express'),
    router  = express.Router();

router.use(init);

function init (req, res, next) {
  req.appData = req.appData = {};
  next();
}

// SESSION routes setup the sessionInfo for subsequent routes
var sessionRoutes = require('./session.routes');
router.use('/sessions', sessionRoutes);

// MEMBER routes rely on the data loaded by the SESSION routes.
var memberRoutes = require('./member.routes');
router.use('/members', memberRoutes);

// MESSAGES routes should only be loaded or executed if MEMBER has not stopped them!
var messagesRoutes = require('./message.routes');
router.use('/messages', messagesRoutes);

module.exports = router;

member.routes.js

var _       = require('lodash'),
    express = require('express'),
    models  = require('../data/models'),
    router  = express.Router();
    
router.use(init);
router.param('id', loadMember);
router.get('/:id', sendMember);

function init (req, res, next) {
  models.Member.findById(req.sessionInfo.memberId, function(err, member){
    if (err) { return next(err); }
    req.sessionInfo.member = member;
    next();
  });
}

function loadMember (req, res, next, id) {
  if (req.sessionInfo.memberId === id) {
    req.appData.member = req.sessionInfo.member;
    return next();
  }
  models.Member.findById(id, function(err, member){
    if (err) { return next(err); }
    req.appData.member = member;
    next();
  });
}

function sendMember (req, res, next) {
  var info = _.omit(req.appData.member, ['salt', 'hash']) || {};
  res.send(info);
}

module.exports = router;

message.routes.js

var _       = require('lodash'),
    express = require('express'),
    models  = require('../data/models'),
    router  = express.Router();
    
router.use(init);
router.param('id', loadMessage);
router.get('/', sendMessageList);
router.get('/:id', sendMessage);

function init (req, res, next) {
  models.Message.findUnreadMessages(req.sessionInfo.memberId, function(err, unreadMsgs){
    if (err) { return next(err); }
    req.appData.messages = req.appData.messages || {};
    req.appData.messages.undread = unreadMsgs;
    next();
  });
}

function loadMessage (req, res, next, id) {
  req.appData.message = _.find(req.appData.messages.unread, function(msg){
    return (msg.id == id);
  });
  if (req.appData.message) { return next(); }
  models.Message.findById(id, function(err, message){
    if (err) { return next(err); }
    req.appData.message = message;
    next();
  });
}

function sendMessage (req, res, next) {
  var info = _.omit(req.appData.member, ['audit']) || {};
  res.send(info);
}

module.exports = router;

session.routes.js

var express = require('express'),
    router  = express.Router();
    
router.use(init);
router.use(validateSession);

function init (req, res, next) {
  req.sessionInfo = req.sessionInfo || {};
  // Decode req.headers.authorization into req.sessionInfo
  // Member ID is now stored in:  req.sessionInfo.memberId
  next();
}
function validateSession (req, res, next) {
  var now = new Date();
  if (req.sessionInfo.expiryDate <= now) { return next('Session has expired'); }
  next();
}

module.exports = router;