01. Introduction

In modern web development, Cross-Origin Resource Sharing (CORS) is essential for ensuring secure data exchanges between different domains. However, developers often encounter CORS errors when building frontend and backend systems. This blog explains what CORS is and provides a practical solution to fixing CORS errors in a Vite-based project.

02. What is CORS?

CORS stands for Cross-Origin Resource Sharing. It is a security feature implemented by web browsers to restrict how resources from one domain (origin) can be requested by another. While this is important for security, it can sometimes block legitimate requests in modern web applications.

A typical example is a frontend application hosted on http://localhost:3000 trying to communicate with a backend API at https://api.example.com. If the server does not explicitly allow cross-origin requests, the browser will block the request and throw a CORS error.

03. Understanding CORS Errors

A CORS error occurs when the browser blocks a request due to missing or incorrect cross-origin permissions. The error often appears in the developer console as:

Access to XMLHttpRequest at 'https://api.example.com' from origin 'http://localhost:3000' has been blocked by CORS policy:
No 'Access-Control-Allow-Origin' header is present on the requested resource.
        

The solution lies in configuring either the server or the client to handle cross-origin requests appropriately.

04. Fixing CORS in Vite

In Vite, you can solve CORS errors on the client side by setting up a proxy. This intercepts requests and forwards them to the backend API as if they originated from the same domain.

Here's an example configuration in the vite.config.js file:

server: {
    proxy: {
        '/api': {
            target: 'https://api.example.com',
            changeOrigin: true,
            secure: false,
        },
    },
},
        

In this setup:

• /api: The prefix for API requests in the frontend.
• target: The URL of the backend server.
• changeOrigin: Ensures the request appears to come from the target domain.
• secure: Allows HTTPS requests even if the server uses a self-signed certificate.

Now, you can send requests to /api/endpoint in your frontend code without worrying about CORS.

05. Example: Sending Requests in React

Here's an example of sending a POST request in a React component:

import axios from 'axios';

function loginUser() {
    const formData = {
        username: 'user@example.com',
        password: 'password123',
    };

    axios.post('/api/login', formData)
        .then((response) => {
            console.log('Login successful:', response.data);
        })
        .catch((error) => {
            console.error('Login failed:', error);
        });
}

export default function Login() {
    return (Login
    );
}
        

With the proxy configured in Vite, /api/login will be forwarded to the target backend.

06. Conclusion

CORS errors can be a significant obstacle in web development. By leveraging Vite's proxy feature, you can simplify the process of resolving these issues on the client side. This method not only eliminates the errors but also ensures a seamless experience for developers working with multiple environments.

Start using this approach today to streamline your development workflow!