How to Save Binary Data with JavaScript without Changing Bytes

Learn how to properly save binary data received from a backend in JavaScript without any modifications to the byte structure.
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Understanding the Problem of Saving Binary Data with JavaScript

Saving binary data correctly can often be a challenging task for developers, especially when dealing with communication between a backend and a frontend environment. A common issue arises when the binary data transmitted from a backend (in this case, a Python Flask application) gets altered during the process, leading to unexpected results when saved on the client-side.

The Scenario

In our specific case, we have a Python backend utilizing Flask's send_file function to send binary data to the frontend. This data, however, changes when saved by a JavaScript function, leading to a corrupted file.

Here's a brief overview of the backend code functioning to send binary data:

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

The function retrieves saved character data and sends it as a binary file. However, when this file is downloaded using JavaScript, the bytes change unexpectedly, causing issues with the integrity of the saved file.

The Solution

Luckily, resolving this issue is relatively straightforward with the correct approach to handle binary data in JavaScript. Here’s a step-by-step guide to ensure the binary data remains intact from backend to frontend.

Step 1: Set the Response Type in Axios

The first thing you need to do is modify the Axios request to correctly interpret the binary data received. By default, Axios treats responses as JSON, which can lead to errors when handling binary data.

To fix this, specify the response type as blob when making the request:

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

This tells Axios to handle the response as a Blob, ensuring that the binary data won’t be altered during the process.

Step 2: Create the Object URL for the Blob

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

This way, you ensure that the Blob is used correctly when creating the downloadable link.

Final Download Function

Putting it all together, your function to download the file should look like this:

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

Conclusion

By implementing these changes, you should be able to download binary data from your Python backend without any modifications to the bytes. This approach ensures that your files remain intact, preserving the necessary structure and data integrity that is essential for your application.

If you find yourself struggling with similar issues in the future, remember to always check how your data is being transmitted and handled on both the backend and frontend. Happy coding!