Скачать или смотреть Resolving CORS Issues in NestJS: How to Properly Enable Cross-Origin Requests

Struggling with CORS in your NestJS and React application? Discover how to easily enable CORS to connect your front-end and back-end without facing errors.
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Resolving CORS Issues in NestJS: How to Properly Enable Cross-Origin Requests

If you're developing a web application with a React front-end and a NestJS back-end, you may encounter CORS (Cross-Origin Resource Sharing) errors. This can be particularly frustrating as it prevents your front-end from communicating with the back-end server. In this guide, we'll address a common issue related to CORS and provide a straightforward solution for enabling it effectively.

Understanding the CORS Problem

While trying to connect your React application hosted on http://localhost:3001 to your NestJS API on localhost:3500, you may see a CORS error message in your browser's console and network tab. This error indicates that your request is blocked by the CORS policy due to the different origins of your front-end and back-end.

Here’s a snippet of what the error might look like:

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This issue arises because your browser adheres to the same-origin policy, which restricts web pages from making requests to a different origin (protocol, domain, and port) than the one that served the original web page.

Solution: Properly Enable CORS in NestJS

To resolve the CORS issue in your NestJS application, you need to ensure the API requests from your React application are permitted. Below, we will explore step-by-step solutions to enable CORS correctly.

Step 1: Use the Correct URL Scheme

The first thing to check is the URL you are using in your API request. If you are calling the API endpoint like this:

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you might face issues because this URL lacks a proper scheme (like http or https). Instead, ensure you format your request as follows:

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This small change often resolves many common issues.

Step 2: Enable CORS in Your NestJS Application

Once you have the right URL format, the next step is to enable CORS in your NestJS application.

Basic CORS Setup:

You can start with a simple CORS setup by using the enableCors method directly in your main application file. Here’s how to do it:

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Custom CORS Options:

If you need more control over your CORS settings (for example, allowing specific headers and origins), you can define custom CORS options:

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Advanced CORS Middleware:

If you prefer a more manual approach or require additional middleware logic, you can implement a custom middleware function:

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Step 3: Verify the Changes

After implementing the above changes, test the connection between your React application and your NestJS API. Open your browser’s developer tools and check the network tab and console for any remaining CORS errors. If you’ve set everything up correctly, your front-end should now be able to communicate seamlessly with the back-end API without any CORS issues.

Conclusion

By following the steps outlined in this guide, you can successfully resolve CORS issues between your NestJS back-end and React front-end applications. Remember to always check the request URL format and appropriately configure CORS settings in your NestJS application. With these adjustments, you should be well on your way to developing your integrated web application without hinderances!

If you found this guide helpful, feel free to share it with other developers facing similar challenges!