Getting Started with Express.js

A Complete Guide to Servers, Routing, and Handling Requests in Node.js

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Introduction

When developers first start working with Node.js, they often use the built-in http module to create servers. While powerful, it quickly becomes complex and repetitive for real-world applications. Handling routes, parsing requests, and sending responses manually can make code hard to manage.

This is where Express.js comes in.

Express.js is a lightweight framework built on top of Node.js that simplifies server development. It provides a clean and structured way to handle routes, requests, and responses, making backend development faster and more efficient.

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What Express.js Is

Express.js is a web framework for Node.js that helps you build servers and APIs easily.

Key Idea

Instead of writing low-level code using the Node.js http module, Express provides higher-level abstractions that make development simpler.

What Express Provides

• Easy routing system

• Middleware support

• Simplified request and response handling

• Cleaner and more readable code

Example

import express from "express";

const app = express();

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

app.listen(3000);

With just a few lines, you have a working server.

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Why Express Simplifies Node.js Development

Using raw Node.js can quickly become complicated, especially as your application grows.

Raw Node.js Example

import http from "http";

const server = http.createServer((req, res) => {
  if (req.url === "/" && req.method === "GET") {
    res.end("Home Page");
  }
});

server.listen(3000);

Problems with Raw Node.js

• Manual routing logic

• Hard to scale

• Repetitive code

• Difficult to maintain

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Express Solution

app.get("/", (req, res) => {
  res.send("Home Page");
});

Benefits

• Cleaner syntax

• Built-in routing

• Easy scalability

• Better code organization

Express abstracts away low-level details so you can focus on building features.

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Creating Your First Express Server

Setting up an Express server is simple.

Step 1: Install Express

npm install express

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Step 2: Create Server

import express from "express";

const app = express();

app.listen(3000, () => {
  console.log("Server running on port 3000");
});

What Happens

• Express creates an application instance

• app.listen() starts the server

• Server listens for incoming requests

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Handling GET Requests

GET requests are used to retrieve data from the server.

Example

app.get("/users", (req, res) => {
  res.send("List of users");
});

Explanation

• /users is the route

• app.get() handles GET requests

• req contains request data

• res is used to send response

Use Cases

• Fetching user data

• Retrieving products

• Loading pages

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Handling POST Requests

POST requests are used to send data to the server.

Example

app.use(express.json());

app.post("/users", (req, res) => {
  const user = req.body;
  res.send(`User ${user.name} created`);
});

Explanation

• express.json() parses JSON body

• req.body contains client data

• Server processes and responds

Use Cases

• Creating new users

• Submitting forms

• Sending data to server

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Sending Responses

Express provides multiple ways to send responses.

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1. Sending Text

res.send("Hello World");

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2. Sending JSON

res.json({ message: "Success" });

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3. Sending Status Codes

res.status(200).send("OK");

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Why This Matters

• Clear communication with client

• Structured responses

• Better API design

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Routing Concept in Express

Routing is how the server decides what to do when a request is received.

Basic Idea

Each route consists of:

• HTTP method

• URL path

• Handler function

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Example

app.get("/", (req, res) => {
  res.send("Home");
});

app.get("/about", (req, res) => {
  res.send("About Page");
});

How It Works

• Request comes to server

• Express matches route

• Corresponding handler executes

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Request → Route Handler → Response Flow

Client → Request → Express Router → Route Handler → Response → Client

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Express Routing Structure Visualization

app
 ├── GET /users
 ├── POST /users
 ├── GET /products
 └── DELETE /users/:id

Each route handles a specific operation.

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Real-World Example

app.get("/users", (req, res) => {
  res.json([{ id: 1, name: "John" }]);
});

app.post("/users", (req, res) => {
  res.status(201).json({ message: "User created" });
});

This is how real APIs are built using Express.

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Key Takeaways

• Express is a framework built on Node.js

• Simplifies server and API development

• Provides clean routing system

• Handles requests and responses easily

• Essential for backend development

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Conclusion

Express.js makes backend development in Node.js simple, structured, and scalable. By abstracting low-level details, it allows developers to focus on building features instead of handling boilerplate code.

Understanding Express is a crucial step in becoming a full-stack developer. Once you master it, you can build APIs, integrate databases, and create production-ready applications efficiently.

The next step is to combine Express with middleware, authentication, and databases to build complete backend systems.