req.query for query strings in Express - Mini Project: Build & Apply

Using req.query to Read Query Strings in Express

📖 Scenario: You are building a simple Express server that responds to requests with personalized messages based on query strings in the URL.

🎯 Goal: Learn how to use req.query in Express to read query string parameters and use them in your response.

📋 What You'll Learn

Create an Express app with a GET route at /greet

Use req.query to read the name parameter from the URL

Send a greeting message that includes the name value

Add a default greeting if name is not provided

💡 Why This Matters

🌍 Real World

Web servers often use query strings to get information from users without needing forms. For example, search pages or filters use query strings.

💼 Career

Understanding how to read query strings with req.query is essential for backend developers working with Express to build APIs and web applications.

1

Set up Express app and route

Create an Express app by requiring express and calling express(). Then create a GET route at /greet with a callback function that takes req and res as parameters.

Express

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

// Your code here

Need a hint?

Remember to require Express and create an app instance before defining routes.

2

Read the name query parameter

Inside the /greet route callback, create a variable called name and set it to req.query.name to read the name query string parameter.

Express

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

app.get('/greet', (req, res) => {
  // Create a variable called name and assign req.query.name
  // Your code here
});

Need a hint?

Use req.query to access query string parameters by name.

3

Send a greeting message using the name parameter

Still inside the /greet route, use res.send() to send a message that says Hello, {name}! if name exists. If name is missing, send Hello, guest! instead.

Express

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

app.get('/greet', (req, res) => {
  const name = req.query.name;
  // Send greeting message using res.send()
  // Your code here
});

Need a hint?

Use an if statement to check if name exists and send the appropriate message.

4

Start the server on port 3000

Add app.listen(3000) to start the Express server on port 3000.

Express

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

app.get('/greet', (req, res) => {
  const name = req.query.name;
  if (name) {
    res.send(`Hello, ${name}!`);
  } else {
    res.send('Hello, guest!');
  }
});

// Start the server on port 3000
// Your code here

Need a hint?

Use app.listen(3000) to start the server on port 3000.