Express.js app entry point

Question

It appears some route middleware is running before index.js, which is crashing my application because the order of execution prevents me from loading my dotenv file on time.

I would like to load my dotenv file before everything in order to make sure that all modules that require it will have access to it.

However, while debugging this issue, I noticed that a console.log at the top of the app entry point still doesn't log first.

Folder structure:

src
------index.js
middleware
------auth.js
routes
------auth.route.js
------index.js
.env

Code that logs first middleware/auth.js:

import { Strategy as JwtStrategy, ExtractJwt } from 'passport-jwt'

module.exports = function() {
  console.log('this prints first with undefined', process.env.JWT_SECRET) <-------

which gets called in auth.route.js

import auth from '../middleware/auth'

const userRouter = express.Router()

userRouter.get('/dashboard', auth().authenticate(), function(req, res) {
  res.send('Authenticated, user id is: ' + req.user.id)
})

index.js file:

console.log("this prints second");                        <---------
(...)
import routes from './routes'
import express from 'express'
import auth from './middleware/auth'

require('dotenv').config({ silent: process.env.NODE_ENV === 'production' })

const app = express();
(...)
app.use('/api', routes);

Answer 1

It's not clear from the code fragments in your question where the problem, because I think you've omitted the place where you import the auth.route.js module.

The answer that follows assumes that you actually import auth.route.js in the index.js file, probably before importing middleware/auth (which isn't actually used in the code fragment you posted). So, based on that assumption, here's what's probably happening:

The thing to keep in mind is that code in a module is executed when it is imported. This doesn't affect middleware/auth at first, since all it does is declare a function. But it does affect auth.route.js - look at what that module does:

It imports the auth function from middleware/auth module, which calls the userRouter.get() function. One of the arguments to that function is a call to the auth() function.

If you're importing auth.route.js in your code (and I suspect you are), then that's where the auth function is getting called prematurely.

Now, how to fix this? It's actually pretty easy: the auth.route.js file should export a function which is called to initialize the routes when you're ready, like this:

auth.route.js

import auth from '../middleware/auth'

const userRouter = express.Router()

export default () => {
  userRouter.get('/dashboard', auth().authenticate(), function(req, res) {
    res.send('Authenticated, user id is: ' + req.user.id)
  })

  return userRouter;
}

And when you're ready to initialize the routes (ie. when everything else is set up).

import getRouter from './modules/auth.route.js';

app.use('/api', getRouter());