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This guide explains how to download files from a Node.js server using ReactJS. Learn about the importance of setting `responseType` to blob to avoid corrupted downloads.
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How to Properly Download Files in ReactJS from Node.js

Downloading files in a web application can sometimes be tricky, especially when you're working with different technology stacks. If you're developing an application using ReactJS for the frontend and Node.js for the backend, you might encounter issues when attempting to download files. In this guide, we will discuss a common problem faced during file download and how to effectively solve it.

The Problem: Corrupted File Downloads

Imagine you are developing a ReactJS application and trying to download a file stored on your Node.js server. You may set up an endpoint to handle file downloads, and it works perfectly when accessed directly through the browser. However, when you try to initiate a download through your ReactJS application, you notice that the downloaded file is corrupted and cannot be opened.

In this case, you found yourself in a situation where the content of your PDF file was muddled with strange characters, indicating a problem with how the response data was handled.

The Setup: Node.js Server Code

Let's look at how the Node.js server sends files:

[[See Video to Reveal this Text or Code Snippet]]

In this code, when a GET request is made to /download/:filesaveas, the server sends the requested file for download. This works well when you manually test the endpoint in the browser.

The Attempt: ReactJS Download Function

On the ReactJS client side, you might create a function to download the file when a button is clicked:

[[See Video to Reveal this Text or Code Snippet]]

While the intention is clear, this approach has a critical oversight.

The Solution: Setting responseType to blob

The key to fixing the corrupted file download issue lies in the responseType of the Axios request. When downloading files, you should specify that you're expecting a blob response. Here’s how you can modify your downloadFile function:

[[See Video to Reveal this Text or Code Snippet]]

Changes Made:

Added responseType: 'blob': This tells Axios to treat the incoming data as a binary file, which is essential for non-text files like PDFs.

Changed MIME type for download: Updating the MIME type to "application/pdf" in the download function helps the browser understand the type of file being downloaded.

Conclusion

By adding the responseType: 'blob' in your Axios request, you ensure that the PDF file is handled correctly and downloaded without corruption. This adjustment is crucial when working with binary data in ReactJS applications. With this simple fix, you can now download files seamlessly from your Node.js server!

If you’re facing similar problems or have any questions, feel free to ask in the comments below!