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Always separate app and server files !

This is considered one of the best-practices of working with node/express
Most of us we just combine them in one single file declaration like follows

const express = require('express');

const app = express();
// parse requests of content-type - application/json
// parse requests of content-type - application/x-www-form-urlencoded
app.use(express.urlencoded({ extended: true }));
const httpServer = require('http').createServer(app);

httpServer.listen(PORT, () => {
  console.log(`listening on *:${process.env.PORT}`);
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Well that's not the best we can do

Otherwise: Your API will be accessible for testing via HTTP calls only (slower and much harder to generate coverage reports). It probably won't be a big pleasure to maintain hundreds of lines of code in a single file.

So what's the alternative?

The api declaration and the the network related configuration should be separated to gain us :

  • testing the API in-process without having to perform the network calls
  • Faster testing execution
  • Getting wider coverage metrics of the code
  • Allows deploying the same API under flexible and different network conditions
  • Better separation of concerns and cleaner code

How to do it ?

API declaration should reside in app.js:

var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');

var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

app.use(express.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', indexRouter);
app.use('/users', usersRouter);

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Server network declaration, should reside in /bin/www
const app = require('../app');
const http = require('http');

// Get port from environment and store in Express.
const port = normalizePort(process.env.PORT || '3000');
app.set('port', port);

// Create HTTP server.
const server = http.createServer(app);
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And the global project structure should be like follows

Image description

I hope this was helpful to develop more good habits and best practices !

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