Allow Multiple Cors Domain In Express Js

When it comes to building web applications using Express.js, dealing with Cross-Origin Resource Sharing (CORS) is essential. CORS helps to determine how resources on a web page can be shared across different domains. In this article, we'll dive into how you can allow multiple CORS domains in Express.js to ensure seamless communication between your application and various origins.

To enable multiple CORS domains in Express.js, you can leverage the 'cors' package, a popular middleware that simplifies cross-origin requests handling. First, make sure to install the 'cors' package by running the following command in your terminal:

npm install cors

After installing the package, you can incorporate it into your Express application by requiring it and using it as middleware. Here's how you can do it:

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

const app = express();

// Allow multiple CORS domains
const allowedDomains = ['http://example1.com', 'http://example2.com'];

const corsOptions = {
  origin: function (origin, callback) {
    if (allowedDomains.indexOf(origin) !== -1) {
      callback(null, true);
    } else {
      callback(new Error('Not allowed by CORS'));
    }
  },
};

app.use(cors(corsOptions));

// Your application routes and logic here

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

In the code snippet above, we start by requiring the 'express' and 'cors' packages. We then define an array called `allowedDomains` containing the domains that you want to allow for CORS requests. Next, we set up the `corsOptions` object, specifying a custom origin validation function that checks if the incoming request's origin is included in the `allowedDomains` array.

By calling `app.use(cors(corsOptions))`, we enable CORS with the defined options in our Express application. Now, requests originating from the specified domains will be permitted, while others will be blocked with an error message.

Remember to replace `'http://example1.com'` and `'http://example2.com'` with the actual domains you want to allow for CORS in your application.

With this setup in place, your Express.js application will be able to handle cross-origin requests from multiple domains seamlessly and securely. This approach enhances the interoperability of your web application and fosters a better user experience across various platforms.

In conclusion, incorporating multiple CORS domains in your Express.js application is crucial for facilitating communication between different origins. By following the steps outlined in this article, you can enhance the flexibility and accessibility of your web application while maintaining security standards. So go ahead, implement multiple CORS domains in Express.js, and unlock the full potential of your application!