Set Up an Express.js App with npm and Express Generator

The root route in app.js can return “Hello from Express” as soon as the one-route server is running. That first response makes me curious how little project structure the route needs.

Decide whether to keep the app in one file or use Express Generator’s project tree. Let that choice set how much structure to put around your first route.

Choose a manual app or a scaffold

Express is a Node.js web framework that maps HTTP requests to handlers and sends responses. You can start with one app file, or let Express Generator create a directory structure around it.

I chose the one-file app first because its route and listener stay together, so the first request is visible before a generated tree becomes useful.

An Express Generator project starts with a directory tree, but that tree does not tell you which Express release its manifest depends on. Check the app’s dependency before choosing the next step.

Check Node.js and prepare a project directory

Express 5 requires Node.js 18 or newer, according to the Express installation guide.

• Install Node.js and npm, then make sure both commands are available in your terminal.
• Choose an empty folder for this app.
• Keep a text editor open for the app file.

node --version
npm --version

npm ships with Node.js. If it is missing, reopen a terminal after installing Node.

Build and run a one-route Express app

An Express app needs a route and a listener for the first request, so its handler can answer when the request method and path match.

Step 1: initialize a local project

Run the setup commands in the app folder. npm init writes the manifest, and npm install adds Express to that project.

mkdir express-manual
cd express-manual
npm init -y
npm install express
npm pkg set scripts.start="node app.js"

Step 2: handle the root request

Create app.js and use a port that is free on your machine.

const express = require('express');
const app = express();
const port = 3100;

app.get('/', (req, res) => {
  res.send('Hello from Express');
});

app.listen(port, () => {
  console.log(`Listening at http://localhost:${port}`);
});

Express matches app.get against both GET and /. The handler sends its text through the response object, which ends that request.

I kept the response short so the status and body fit in the same terminal result.

Step 3: start the server and inspect its response

Start the app from its project folder and leave that terminal open. Request the root path from another terminal.

npm start

curl -sSi http://127.0.0.1:3100/

HTTP 200 and Hello from Express confirm the route answered, but they do not establish that the app is ready for deployment.

Generate a larger project when you need the folders

Express Generator creates a starter tree, but its package version and the Express runtime are separate decisions. I left views out because the first route does not render a template.

Step 1: create a view-free scaffold

The Express Generator documentation lists its command-line options. This command creates a public folder and separate route files without a view engine.

npx --yes express-generator --no-view express-no-view-run

• app.js configures the application and mounts middleware and routes.
• bin/www starts the HTTP server and reads its port from the environment.
• routes holds the sample route modules.
• public holds static files such as the generated index page and stylesheet.

Step 2: check and replace the generated dependencies

The generated manifest selected an Express 4 dependency. I kept its file tree but changed the package versions before using the app.

A newer generator CLI does not mean the generated app uses a newer Express runtime.

I removed and reinstalled Express and Morgan without release tags, so npm resolved Express 5.2.1 and Morgan 1.12.1. npm audit –omit=dev then reported zero vulnerabilities.

cd express-no-view-run
npm install
npm uninstall express morgan
npm install express morgan
npm audit --omit=dev

Step 3: run the scaffold on a free port

The generated launcher listens on port 3000 unless PORT is set.

PORT=3101 npm start
curl -sS -o /dev/null -w 'HTTP %{http_code}\n' http://127.0.0.1:3101/

HTTP 200 confirms the generated route served its static page. The project still needs application-specific tests before it handles untrusted traffic.

Fix the setup errors that stop the server

Use the failure type to choose what to inspect before changing route code.

Express selects a handler by HTTP method and path. The routing guide explains the match when you add another endpoint.

Keep the first route small until it needs more structure

Keep the one-route app until another module or a view solves a concrete need, then run npm ls express before adding another package.

npm ls express

Express app setup FAQ

These answers cover the setup questions that remain after the first route responds.