Why understanding res matters in Express - See It in Action

Why understanding res matters

📖 Scenario: You are building a simple Express server that sends responses to users. Understanding how the res object works is important to send the right messages back.

🎯 Goal: Build a basic Express server that uses the res object to send a text message and a JSON response to the client.

📋 What You'll Learn

Create an Express app variable called app

Create a route handler for GET requests on /hello

Use res.send() to send a plain text message

Create a route handler for GET requests on /data

Use res.json() to send a JSON object

💡 Why This Matters

🌍 Real World

Express servers are used to build web applications and APIs that send data and pages to users. Knowing how to use <code>res</code> helps you control what users see.

💼 Career

Backend developers must understand how to send correct responses using <code>res</code> in Express to build reliable and user-friendly web services.

1

Set up Express app

Create a variable called express that requires the 'express' module. Then create a variable called app by calling express().

Express

const express = require('express');
const app = express();
// Your code here

Need a hint?

Use require('express') to import Express and then call it to create the app.

2

Add a simple text response route

Add a GET route handler on /hello using app.get. The handler function should take req and res as parameters. Use res.send() to send the text message 'Hello, world!'.

Express

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

app.get('/hello', (req, res) => {
  // Your code here
});

Need a hint?

Use app.get('/hello', (req, res) => { res.send('Hello, world!'); }) to send a text response.

3

Add a JSON response route

Add a GET route handler on /data using app.get. The handler function should take req and res as parameters. Use res.json() to send the JSON object { message: 'This is JSON data' }.

Express

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

app.get('/hello', (req, res) => {
  res.send('Hello, world!');
});

app.get('/data', (req, res) => {
  // Your code here
});

Need a hint?

Use res.json({ message: 'This is JSON data' }) to send JSON data.

4

Start the Express server

Add code to start the server by calling app.listen on port 3000. Use a callback function that logs 'Server running on port 3000'.

Express

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

app.get('/hello', (req, res) => {
  res.send('Hello, world!');
});

app.get('/data', (req, res) => {
  res.json({ message: 'This is JSON data' });
});

// Your code here

Need a hint?

Use app.listen(3000, () => { console.log('Server running on port 3000'); }) to start the server.