How to Successfully Download a ZIP File Using NodeJS and ReactJS

Struggling to download ZIP files in your React app? Learn how to properly handle POST responses from a NodeJS backend to ensure successful file downloads.
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How to Successfully Download a ZIP File Using NodeJS and ReactJS

Downloading files, especially ZIP files, can sometimes become a tedious task for developers. When working with a backend implemented in NodeJS and a frontend in ReactJS, it’s essential to ensure the data flow and response handling is correctly set up for a seamless user experience. This post addresses the common problem faced while trying to download ZIP files from a NodeJS backend in a React application, particularly when the downloaded file ends up being corrupted or unreadable.

The Problem

You may find yourself in a situation where your ReactJS client attempts to download a ZIP file that has been created on the backend, but the resulting file is not opening correctly. The backend appears to function correctly, saving a file that can be opened, but the React client’s response management is not producing the expected results.

For example, you might be seeing a console output with ASCII sequences from what should be a ZIP file, but no ZIP application can open it. This generally suggests issues with how the client-side is processing the response received from the backend.

Understanding the Backend Setup

Let’s look at the backend method responsible for generating the ZIP file. The provided method creates a ZIP file with specific documents retrieved from a database, utilizes the AdmZip package to construct the ZIP, and finally sends it back as a response.

Here’s a simplified version of that backend function’s logic:

Authenticate the user and retrieve document IDs from the request.

Generate a new ZIP file using AdmZip.

Add files to the ZIP.

Send the ZIP file back to the client with appropriate headers.

The Solution

Handling the Response in ReactJS

The solution to the problem lies in how you handle the response from your API call in React. Instead of directly using the response data, you need to create a Blob from the response, ensuring that you specify the correct response type.

Here’s how you can achieve that:

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

Explanation of the Code

Setting Response Type: The key here is to specify responseType: 'arraybuffer' in your POST request configuration. This tells Axios (or the HTTP client in use) to return the response in the form of an ArrayBuffer, which is suitable for binary data like ZIP files.

Creating a Blob: Upon receiving the response, we create a new Blob with the data received, specifying its type as application/octet-stream.

Downloading the File: Finally, we call saveAs (from the file-saver library) with the Blob and the desired filename to trigger the file download in the browser.

Conclusion

By adjusting how you handle the response in your React application, you can successfully download ZIP files generated by your NodeJS backend. Ensuring that your API requests and responses are appropriately managed is crucial to preventing file corruption and enhancing user experience.

Don't hesitate to test these code adjustments in your application; you'll likely find the modification solves the file download issue you're currently facing! If you experience further troubles, make sure to review both client and server-side logs for any additional clues.