How can multiple files be sent from Axios to NestJS, and why does the error 'Multipart: Boundary not found' occur?

How can one effectively send multiple files from Axios to a NestJS backend, ensuring proper configuration and handling of multipart/form-data requests, and what are the common pitfalls and troubleshooting steps to address the 'Multipart: Boundary not found' error, including best practices for setting headers and structuring the request payload?

Steps to Send Multiple Files from Axios to NestJS Prepare the Data:

Collect the files you need to send and create a FormData object. This object allows you to append multiple files and any additional data you need to send.

Configure Axios Request:

Ensure that your Axios request is set up correctly to handle multipart/form-data. Axios will automatically set the correct headers for this type of data, so you generally don't need to set them manually.

Send the Request:

Use Axios to send the request to your NestJS backend. The request will include the files and any other data appended to the FormData object.

Common Pitfalls and Troubleshooting Steps Boundary Not Found Error:

This error typically occurs when the boundary parameter in the Content-Type header is missing or incorrect. To avoid this, let Axios automatically set the Content-Type header for multipart/form-data. Manually setting this header can result in missing the necessary boundary parameter.

Proper File Handling on the Backend:

Ensure that your NestJS backend is configured to handle multipart/form-data requests. This typically involves using middleware such as Multer to parse the incoming files and save them to the desired location.

Best Practices Use FormData:

Always use the FormData object for handling file uploads. It provides a convenient way to manage multiple files and any additional data.

Automated Header Management:

Allow Axios to manage the Content-Type header for multipart/form-data. This prevents issues related to missing or incorrect boundary parameters.

Test with Tools:

Use tools like Postman to test your API endpoints and ensure that the requests are formatted correctly and the backend is handling them as expected.

Debugging and Logging:

Implement logging on both the client and server sides to help diagnose issues. This can include logging the data being sent and received, as well as any errors encountered during processing.