How to Download Files via POST with JSON in JavaScript/jQuery?

Downloading Files via POST with JSON in JavaScript/jQuery

When dealing with RESTful web services, handling responses can vary depending on their format. This article explores a specific scenario where the objective is to submit a POST request with JSON data and retrieve a downloadable file in response, prompting the browser to save it.

Solution #1: iframe Injection

One approach is to create an iframe and append its source to the body of the web page. This will trigger the browser's download prompt. However, it is important to note that this method can interfere with existing page content, so using appendChild instead of innerHTML is recommended.

<code class="javascript">$.post('/create_binary_file.php', postData, function(retData) {
  var iframe = document.createElement("iframe");
  iframe.setAttribute("src", retData.url);
  iframe.setAttribute("style", "display: none");
  document.body.appendChild(iframe);
});</code>

Solution #2: jQuery Append

A jQuery-based alternative is to use the append() method to add the iframe to the body.

<code class="javascript">$.post('/create_binary_file.php', postData, function(retData) {
  $("body").append("<iframe src='" + retData.url+ "' style='display: none;' ></iframe>");
});</code>

Mechanism

Both solutions rely on the assumption that the POST response includes a 'url' property pointing to the downloadable file. When the iframe is added to the page with that URL, the browser intercepts the request and prompts the user to download the file. This approach requires proper MIME type configuration on the web server.

Evaluation

While these solutions provide a viable approach to downloading files via POST requests, it is crucial to consider potential limitations and drawbacks, especially when dealing with larger files. Additionally, it may be necessary to implement additional functionality in theAJAX success handler to enable error handling and provide feedback to the user.

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