Why error handling is critical in Express - See It in Action

Why error handling is critical in Express

📖 Scenario: You are building a simple Express server that responds to user requests. Sometimes, things can go wrong, like a missing page or a server problem. Proper error handling helps your server respond nicely instead of crashing or confusing users.

🎯 Goal: Build a basic Express server that includes error handling middleware to catch and respond to errors gracefully.

📋 What You'll Learn

Create an Express app with a route that triggers an error

Add a variable to hold the error message

Use error handling middleware to catch errors

Send a proper error response to the client

💡 Why This Matters

🌍 Real World

Error handling in Express is critical to keep web servers stable and provide clear feedback to users when something goes wrong.

💼 Career

Understanding error handling is essential for backend developers to build reliable and user-friendly web applications.

1

Set up Express app with a route that triggers an error

Create an Express app by requiring express and calling express(). Then create a route /error that throws an error with the message 'Something went wrong!'.

Express

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

// Your code here

Need a hint?

Use app.get to create the route and call next() with an error.

2

Add a variable to hold the error message

Create a variable called errorMessage and set it to the string 'An unexpected error occurred.'.

Express

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

app.get('/error', (req, res, next) => {
    const err = new Error('Something went wrong!');
    next(err);
});

// Your code here

Need a hint?

Just create a constant variable with the exact name and value.

3

Add error handling middleware

Add error handling middleware using app.use with four parameters: err, req, res, next. Inside, set the response status to 500 and send a JSON object with a key error and value errorMessage.

Express

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

app.get('/error', (req, res, next) => {
    const err = new Error('Something went wrong!');
    next(err);
});

const errorMessage = 'An unexpected error occurred.';

// Your code here

Need a hint?

Error handling middleware has four parameters and must be added after routes.

4

Start the server to complete the app

Add app.listen to start the server on port 3000 and add a callback that logs 'Server running on port 3000'.

Express

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

app.get('/error', (req, res, next) => {
    const err = new Error('Something went wrong!');
    next(err);
});

const errorMessage = 'An unexpected error occurred.';

app.use((err, req, res, next) => {
    res.status(500).json({ error: errorMessage });
});

// Your code here

Need a hint?

Use app.listen with port 3000 and a callback that logs the message.