How to Reliably Execute AJAX Functions on BeforeUnload?

Executing AJAX Functions on BeforeUnload

When developing chat applications, it's crucial to gracefully handle user disconnections. One method is to execute an AJAX function upon the user closing the page to remove the corresponding database entry.

In the provided code, the onbeforeunload event is triggered when the user closes the page, and the closeSession() function is executed. This function attempts to send an AJAX request to chat.php to execute a SQL DELETE statement and remove the user's entry from the queue table. However, the request is set to async (the default for jQuery), causing the browser to continue unloading without waiting for the request to complete.

To resolve this, the async option in the AJAX settings should be set to false. This forces the browser to wait for the request to finish before unloading. However, it's important to note that relying on this approach may not always be reliable across different browsers and versions.

Here's the modified code with async set to false:

<code class="js">window.onbeforeunload = closeSession;

function closeSession() {
  $.ajax({
    url: "/chat/process/chat.php",
    type: "GET",
    async: false,
  });

  return "disconnected";
}</code>

By setting async to false, the browser will pause the unloading process until the AJAX request is completed, ensuring that the user's database entry is removed upon disconnection.

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