React Native CORS Origin

Introduction

Cross-Origin Resource Sharing (CORS) is a security feature implemented in web browsers to restrict web pages from making requests to a different domain than the one that served the original web page. It is a mechanism that allows many resources (e.g., fonts, JavaScript, etc.) on a web page to be requested from another domain outside the domain the resource originated from. React Native has made it easier for developers to build mobile applications for multiple platforms. However, when it comes to working with web APIs, CORS issues become a major problem.

What is CORS and Why CORS Origin is Important?

CORS is a security policy enforced by web browsers to restrict web pages from making requests to a different domain than the one that served the original web page. The SOP (Same-origin policy) keeps data from different origins separated so that malicious scripts cannot exploit information from another domain. CORS allows the web page to make HTTP requests to external domains outside the domain the resource originated from. The web server instructs the browser to provide additional security headers during the request/response. Without these headers, the browser blocks the response.

In React Native, we often use APIs to request data from external sources, and thus we need to make cross-origin HTTP requests. If the server doesn't allow CORS or doesn't support CORS headers, the browser blocks the response. We need to ensure that the back-end server provides the necessary headers, which is where CORS Origin comes in.

How to handle CORS Origin in React Native?

To handle CORS Origin in React Native, we need to set the necessary headers in the back-end server. There are several ways to set up CORS headers:

1. Manually

You can manually set the necessary headers in the back-end server to enable CORS. The necessary headers are:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept

These headers instruct the browser to allow cross-origin requests and to allow certain HTTP methods and headers.

2. Using a middleware

Most web frameworks provide middleware that makes it easy to set up CORS headers. For example, in Express.js, you can use the cors middleware:

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

app.use(cors());

This will enable CORS for all routes in your Express.js app.

3. Using a proxy

You can also set up a proxy in your React Native app to bypass CORS restrictions. This can be done by configuring the development server to proxy certain requests. Here's an example of how to set up a proxy in React Native using http-proxy-middleware:

const proxy = require('http-proxy-middleware');

module.exports = function(app) {
    app.use(
        '/api',
        proxy({
            target: 'http://localhost:3000',
            changeOrigin: true,
        })
    );
};

This will proxy all requests to /api to http://localhost:3000, which is the back-end server.

Conclusion

In summary, CORS is a security feature enforced by web browsers to restrict web pages from making requests to a different domain than the one that served the original web page. To handle CORS Origin in React Native, we need to set the necessary headers in the back-end server. We can set these headers manually, use a middleware, or set up a proxy. By doing so, we can enable cross-origin resource sharing and make HTTP requests to external domains.