CORS configuration in Node.js - Mini Project: Build & Apply

CORS Configuration in Node.js

📖 Scenario: You are building a simple Node.js server that will serve data to a frontend running on a different domain. To allow the frontend to access your server's resources, you need to configure CORS (Cross-Origin Resource Sharing) properly.

🎯 Goal: Set up a Node.js server using Express and configure CORS to allow requests only from http://example.com.

📋 What You'll Learn

Create a basic Express server

Install and use the cors middleware

Configure CORS to accept requests only from http://example.com

Add a simple GET route that returns a JSON message

💡 Why This Matters

🌍 Real World

Many web applications have frontend and backend on different domains. Configuring CORS properly allows secure communication between them.

💼 Career

Backend developers often need to configure CORS to enable frontend apps to access APIs safely and correctly.

1

Set up Express server

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

Node.js

# Your code here

Need a hint?

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

2

Import and configure CORS middleware

Create a variable called cors that requires the cors package. Then create a variable called corsOptions that is an object with the key origin set to the string 'http://example.com'.

Node.js

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

Need a hint?

Use require('cors') to import CORS and define corsOptions with the origin set to 'http://example.com'.

3

Apply CORS middleware with options

Use app.use() to apply the cors middleware with the corsOptions object as its argument.

Node.js

const express = require('express');
const app = express();
const cors = require('cors');
const corsOptions = { origin: 'http://example.com' };
# Your code here

Need a hint?

Call app.use() with cors(corsOptions) to enable CORS with your settings.

4

Add a GET route and start server

Add a GET route on '/' using app.get() that sends a JSON response with { message: 'Hello from server' }. Then start the server on port 3000 using app.listen().

Node.js

const express = require('express');
const app = express();
const cors = require('cors');
const corsOptions = { origin: 'http://example.com' };
app.use(cors(corsOptions));
# Your code here

Need a hint?

Use app.get() to create the route and app.listen(3000) to start the server.