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Learn how to efficiently download a `Blob` from a Node.js backend in ReactJS, and avoid common pitfalls like incorrect file content.
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How to Download a Blob Received from a Node.js Backend in ReactJS

In today's web development landscape, downloading files from a backend API is a common task. However, when working with binary data such as Blobs from a Node.js backend, developers often run into issues. A common error occurs when the file downloads successfully, but the contents are just "[object Object]". In this guide, we’ll address this problem and provide a clear solution to ensure you can successfully download Blob objects in your ReactJS application.

Understanding the Problem

When you receive a Blob in a response from your Node.js backend, it’s important to handle it correctly. The response might look something like this:

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

If you've tried downloading the file with code similar to the following:

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You might have realized that this doesn’t work as expected. The issue arises because you are attempting to send a Blob directly as part of a JSON response, which is not supported.

The Solution: Properly Encoding and Decoding Blobs

To successfully send a Blob from your Node.js backend to ReactJS, follow these steps:

Step 1: Encode the Blob on the Server Side

Instead of sending the Blob directly, you'll need to encode it into a format that can be safely transported in JSON. The most common approach is to use Base64 encoding. Here’s how you can modify your backend code:

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

Step 2: Decode the Blob on the Client Side

In your ReactJS application, you will need to decode the Base64 string back into a Blob. Here is how you can do it in your React component:

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

Key Takeaways

Encode your Blobs: Use Base64 encoding to convert your Blob data into a string that can be safely sent in a JSON response.

Decode on the client-side: Use atob to decode the Base64 string back into a binary format, then create a new Blob object for downloading.

Browser Compatibility: This method works across different operating systems and browsers, ensuring a smooth user experience.

In conclusion, by following the outlined steps for encoding and decoding Blobs between your Node.js backend and ReactJS frontend, you can avoid common pitfalls and efficiently handle file downloads in your application. Happy coding!