Possible to pass a parameter into Express' app.use() - node.js

Question

I have my Node/Express server running. I have the main server.js file where most of the code is for the server. Now I want to separate out the routes into a separate file. I have done this before using app.use(routes). But the problem is, I want to pass a string in for one of the routes to use.
Here is my server.js code:
// other imports
import routes from './routes.js';
const app = express();
...
const port = Number.parseInt(process.env.PORT, 10) || 3001;
const serverType = process.env.NODE_ENV === 'production' ? 'Production' : 'Test';
const statusMsg = `${serverType} Node server for external facing web server on ${port}`;
// i want `routes` to have access to `statusMsg`
app.use(routes);
Then in routes.js:
import express from 'express';
const router = express.Router();
router.get('/', (req, res) => res.status(200).send(statusMsg);
export default router;
I use serverType and port elsewhere in server.js, else I would just move all that code to routes.js.
Update
Adding in updated routes.js as I understand it with suggestion from jonrsharpe.
import express from 'express';
const router = express.Router();
const createRoutes = (statusMsg) => {
router.get('/', (req, res) => res.status(200).send(statusMsg);
};
export default createRoutes;

Answer 1

You can separate the server logic, routes logic, and business logic (usually inside a separate file called a controller).
inside the server file try blow code:
const express = require('express');
const app = express();
const bodyParser = require('body-parser')
require('dotenv').config();
const connectDB = require('./config/config')
const cookieParser = require('cookie-parser')
const authRoutes = require('./routes/authRoutes')
const categoryRoutes = require('./routes/categoryRoutes')
const cors = require('cors');
connectDB();
app.use(bodyParser.json());
app.use(cookieParser());
app.use(cors());
//Route Mounting
app.use('/', authRoutes);
app.use('/', categoryRoutes);
app.listen(process.env.PORT, ()=>{
console.log(`Server is running on PORT: ${process.env.PORT}`)
})
Then create a separate file authRoute.js and do the following code
const express = require('express')
const { registerUser, loginUser, getAllUsers, logoutUser} = require('../controllers/authController')
const router = express.Router()
const {isAuthenticatedUser, isAuthorizedRoles} = require('../middleware/auth')
router.route('/user/new').post(registerUser);
router.route('/user/login').post(loginUser);
router.route('/users').get(getAllUsers);
router.route('/account/logout').get(logoutUser);
module.exports = router;
lastly to write the business logic create file authController.js and place the following code.
const User = require('../model/userSchema');
const bcrypt = require('bcryptjs');
const jwt = require('jsonwebtoken');
require('dotenv').config();
exports.registerUser = async (req, re, next)=>{
let password = req.body.password;
password = await bcrypt.hash(password, 10);
const newUser = req.body;
newUser.password = password;
try {
const user = await User.create(newUser);
if(user){
res.json({
success:true,
user
});
}
} catch (error) {
console.log(error);
}
}
exports.loginUser = async function(req, res){
const email = req.body.email;
const password = req.body.password;
if(!email || !password){
return res.json({
success:false,
message:'Please provide the email & Password'
})
}
const user = await User.findOne({email:email});
if(!user){
return res.json({
success:false,
message:'user with this email not found in database'
})
}
const isPasswordMatch = await bcrypt.compare(password, user.password);
if(!isPasswordMatch){
return res.json({
success:false,
message:'Your password is wrong...'
})
}
const token = jwt.sign({ _id: user._id }, process.env.JWT_SECRET, { expiresIn: process.env.JWT_EXPIRY_TIME });
res.cookie('token', token, {httpOnly:true, expires:new Date(Date.now() + 60*60*1000 )}).json({
success:true,
message:'You are logged in! Enjoy',
})
}
exports.getAllUsers = async (req, res, next)=>{
res.json({
success:true,
data:[
{
"id":1,
"name":"Yasir",
"qual":"MCS",
"age":32
},
{
"id":2,
"name":"Tabish",
"qual":"BS",
"age":21
},
{
"id":3,
"name":"Ahmed",
"qual":"BSCS",
"age":32
},
{
"id":4,
"name":"Hassan",
"qual":"MCS",
"age":33
}
]
})
}
exports.logoutUser = async (req, res, next)=>{
res.cookie('token', null, {expires:new Date(Date.now())}).json({
success:true,
message:'You are loggedOut',
})
}
This is the way you can have separation of concerns.