CORS configuration in NestJS - Mini Project: Build & Apply

CORS configuration

📖 Scenario: You are building a simple NestJS backend server that will be accessed by a frontend running on a different domain. To allow the frontend to communicate with your backend, you need to configure CORS (Cross-Origin Resource Sharing) properly.

🎯 Goal: Configure CORS in a NestJS application to allow requests only from http://example.com and enable credentials support.

📋 What You'll Learn

Create a basic NestJS application instance

Add a configuration variable for allowed origin

Enable CORS with the allowed origin and credentials option

Complete the main bootstrap function with the CORS setup

💡 Why This Matters

🌍 Real World

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

💼 Career

Backend developers often need to configure CORS in NestJS or other frameworks to enable frontend-backend integration without security issues.

1

Create a NestJS application instance

Write code to create a NestJS application instance called app using NestFactory.create(AppModule).

NestJS

// Create a NestJS application instance called app
// Your code here

Need a hint?

Use const app = await NestFactory.create(AppModule); inside an async bootstrap function.

2

Add a configuration variable for allowed origin

Add a constant variable called allowedOrigin and set it to the string 'http://example.com'.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  // Add allowedOrigin variable here
  // Your code here
}

bootstrap();

Need a hint?

Define const allowedOrigin = 'http://example.com'; inside the bootstrap function.

3

Enable CORS with allowed origin and credentials

Use app.enableCors() with an options object that sets origin to allowedOrigin and credentials to true.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  const allowedOrigin = 'http://example.com';
  // Enable CORS with origin and credentials
  // Your code here
}

bootstrap();

Need a hint?

Call app.enableCors() with an object: { origin: allowedOrigin, credentials: true }.

4

Complete the bootstrap function by starting the server

Add await app.listen(3000); inside the bootstrap function to start the server on port 3000.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  const allowedOrigin = 'http://example.com';
  app.enableCors({ origin: allowedOrigin, credentials: true });
  // Start the server on port 3000
  // Your code here
}

bootstrap();

Need a hint?

Use await app.listen(3000); to start the server.