Middleware with access to app instance

app_access_global.js

var express = require('express');
var app = express();

//Normal way - won't work if function is extracted to a module
app.use(function(req, res, next) {
  'use strict';
  
  app.locals.greeting = 'hello';
  next();
  
});

app_access_global_diff.js

var express = require('express');
var server = express();

//Assuming app will be the server name is bad news
//This won't work
server.use(function(req, res, next) {
  'use strict';
  
  app.locals.greeting = 'hello';
  next();
  
});

app_access_with_safe_module.js

var express = require('express');
var server = express();
var greet = require('./greet_module_safe');

//Should work fine
server.use(greet(server));

greet_module_safe.js

module.exports = function(appInstance) {
  'use strict';
  
  //If this module is run with an instance of the current app then
  //then the module should work despite the server name and be
  //fully independent
  return function(req, res, next) {
    appInstance.locals.greeting = 'hello';
    next();
  };
  
};

greet_module_unsafe.js

module.exports = function(req, res, next) {
  'use strict';
  
  //This should violate use strict since app is not defined here
  app.locals.greeting = 'hello';
  next();
  
};