Express.js Web API Basics

What is Express.js?

Express.js is one of the most popular backend frameworks in Node.js.

It is used for:

• Building APIs
• Creating backend servers
• Handling HTTP requests
• Building web applications

Step 1 - Create Project Folder

Open terminal and create a new folder.

mkdir expressjs-tutorial

Step 2 - Move Inside Folder

cd expressjs-tutorial

Step 3 - Initialize Node.js Project

Run the following command:

npm init -y

Step 4 - Install Express.js

npm install express

Step 5 - Install Nodemon

npm install -D nodemon

Step 6 - Create Source Folder

mkdir src

Step 7 - Import Express

import express from 'express';

Step 8 - Create Express Application

const app = express();

Step 9 - Configure Port

const port = process.env.PORT || 3000;

Step 10 - Create First Route

app.get('/', (req, res) => {

    res.send('Hello World');

});

Step 11 - Start Express Server

app.listen(port, () => {

    console.log(`Running on port ${port}`);

});

Final Working Express.js Application

import express from 'express';

const app = express();

const port = process.env.PORT || 3000;

app.get('/', (req, res) => {

    res.send('Hello World');

});

app.listen(port, () => {

    console.log(`Running on port ${port}`);

});

Advantages of Express.js

Important Tips

• Use nodemon during development
• Keep routes organized
• Practice API development regularly

Interview Answer

Summary

Express.js is one of the easiest and most powerful frameworks for backend development using Node.js.

It helps developers create APIs, manage requests, and build scalable applications easily.