Sanitization methods in Express - Mini Project: Build & Apply

Sanitization Methods in Express

📖 Scenario: You are building a simple Express server that accepts user input from a form. To keep the server safe and clean, you need to sanitize the input data before using it.

🎯 Goal: Create an Express app that sanitizes a user input field called username by trimming spaces and escaping special characters.

📋 What You'll Learn

Create an Express app with a POST route at /submit

Use express-validator sanitization methods to trim and escape the username field

Send back the sanitized username in the response

💡 Why This Matters

🌍 Real World

Sanitizing user input is essential to prevent security issues like cross-site scripting (XSS) and to ensure clean data storage.

💼 Career

Backend developers often use Express and express-validator to build secure APIs that handle user data safely.

1

Setup Express app and body parser

Create an Express app by importing express and calling express(). Use express.json() middleware to parse JSON request bodies.

Express

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

// Your code here

Need a hint?

Remember to import express and create an app instance. Use app.use(express.json()) to parse JSON bodies.

2

Add express-validator import and setup POST route

Import body from express-validator. Add a POST route at /submit that accepts a JSON body.

Express

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

app.use(express.json());

// Your code here

Need a hint?

Import body from express-validator. Create a POST route handler for /submit.

3

Apply sanitization methods to username

Inside the POST route, use body('username').trim().escape() to sanitize the username field. Use req.body.username to access the input.

Express

const express = require('express');
const app = express();
const { body } = require('express-validator');

app.use(express.json());

app.post('/submit', (req, res) => {
  // Sanitize username here
  // Your code here
});

Need a hint?

Use body('username').trim().escape() as middleware in the POST route to sanitize the input.

4

Send back sanitized username in response

Inside the POST route handler, get the sanitized username from req.body.username and send it back in JSON format with key sanitizedUsername.

Express

const express = require('express');
const app = express();
const { body, validationResult } = require('express-validator');

app.use(express.json());

app.post('/submit', [
  body('username').trim().escape()
], (req, res) => {
  // Send response with sanitized username
  // Your code here
});

Need a hint?

Access req.body.username after sanitization and send it back using res.json().