Question

I’m building my node.js app which has the following structure:

• server.js
• controllers/user.js

server.js require the user.js controller with:

require('./controllers/user.js').route(app, mongoose);

the controller/user.js file is like:

function route(app, mongoose){
   function route(app, mongoose){

   // Create new User item
   app.post('/user/create', function(req, res){
     ...
   }

   // Edit user
   app.put('/user/:id/edit', function(req, res){
    ...
   }

   ...
}
module.exports.route = route;

This is working fine.
I know want to had middleware in the Edit user function for instance so it looks like:

...
app.put('/user/:id/edit', loadUser, function(req, res){
...

If I define loadUser function right above this line it’s working fine. When I add all the middleware fonction in a file ‘./lib/middleware.js’ and when I try to load that file in user.js with:

require('../lib/middleware.js').create(); // Create is the exported function

this does not work and I have the error message saying that loadUser is an unknow function.

Any idea ?

** UPDATE **

I have updated the files such that, in server.js (main file) I have:

...
var middleware = require('./lib/middleware.js');
...
require('./controllers/user.js').route(app, mongoose, middleware);
...

In middleware.js, I then have:

function create() {
  function loadUser(req, res, next) {
    // You would fetch your user from the db
    var user = users[req.params.id];
    if (user) {
      req.user = user;
      next();
    } else {
      next(new Error('Failed to load user ' + req.params.id));
    }
  }
return module;
}

In controllers/user.js I have

function route(app, mongoose, middleware){
   ...
   // Modify an user
   app.put('/user/edit', middleware.loadUser, function(req, res){
     ...
   }
   ...
}

When I run the app (node server.js) I then have the following error:

Error: PUT route /user/edit requires a callback

I am not sure to return the correct thing within middleware.js, not really familiar with module stuff yet. I also tried the “module.exports.create = create;” but same thing.

UPDATE WITH ANOTHER TRY

what if I create a module for the function ? In ./lib/middleware.js I would have:

(function(){
  var middleware = {};
  middleware.loadUser = function () {
  console.log("loadUser");
  }
  return middleware;
}());

And in server, I call it:

var middleware = require('./lib/middleware.js');
middleware.loadUser;

It seems to me that should work but it does not…

Answer 1

“global” scope in a file is actually module scope. Just by creating a function in a different file it does become in scope in your original file.

What you want to do instead is

// routes.js
var middleware = require("../lib/middleware.js").create();

app.put('/user/:id/edit', middelware["loadUser"], function(req, res){

You will find that global variables actually write to module in their scope.

Then your function loadUser() { ... } should exist in the module property.

// middleware.js
function create() { 
    ...

    return module;
}

If you return module from your create function your returning global scope.

[Edit]

function create() {
  function loadUser(req, res, next) {
    // You would fetch your user from the db
    var user = users[req.params.id];
    if (user) {
      req.user = user;
      next();
    } else {
      next(new Error('Failed to load user ' + req.params.id));
    }
  }
return module;
}

You either need to add module.loadUser = loadUser or define loadUser in module scope. I.e. outside the create function.

[Further Edit]:

A standard setup would be something like:

// middleware.js
(function() {

    function loadUser(...) {
        ...
    }

    ...

    module.exports.loadUser = loadUser;

})();

//otherfile.js
var middle = require("middleware");
middle.loadUser();