How to Handle Downloadable Files in JavaScript/jQuery Using AJAX Requests?

Downloading Files via POST with JSON Data in JavaScript/jQuery

Scenario:

You have a single-page webapp that communicates with a RESTful web service via AJAX calls. You need to:

• Submit a POST request with JSON data to a REST URL.
• Return JSON if the request specifies a JSON response.
• Return a downloadable binary file if the request specifies a binary response (e.g., PDF, XLS).

Issue:

How to handle downloadable files in the client JavaScript code when using AJAX calls?

Solution:

While the provided code successfully handles JSON responses, it's not directly possible to download files using AJAX requests due to limitations in the dataType option. However, alternative approaches can be taken:

Method 1: Generating and Storing Files on Server

• Make an AJAX request to generate the binary file and return a JSON response with a URL to the file.
• In the AJAX success handler, redirect the browser to the URL using window.location.href to download the file.

Pros:

• Centralized file management on the server.

Cons:

• Requires multiple AJAX calls.
• Additional file management overhead on the server.

Method 2: Creating an Iframe

• Perform a POST request to /create_binary_file.php with the JSON data.
• Create an iframe and set its src attribute to the response from the POST request, which is expected to contain the URL of the downloadable file.
• Add the iframe to the page using document.body.appendChild() or jQuery's $.body.append().

Pros:

• Promotes user interaction for downloading the file.
• No additional file management on the server.

Cons:

• Requires modifying the DOM.

Considerations:

• Method 1 requires more server overhead but allows for more control and file management.
• Method 2 can be simpler but involves modifying the DOM and may not be suitable for complex pages.
• The server must have the appropriate MIME type configuration to facilitate downloading of binary files.

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