Safari does not run callback function on refresh/onbeforeunload on server side (calls client side code)

Question

I am trying to send some requests to the database when the window is unloaded (i.e. when you refresh the page). For some reason, only on Safari, the client side code gets executed, but the request to the server never goes through. When I step through the code manually in the debugger, the server does get the request and processes it fine.

Anyone know why this is happening?

window.onbeforeunload = function() {
  console.log("inside on before unload");
  var requestParam = new a.ListRequest();
  requestParam.setAction('set_delete');
  
  var callback = function(isSuccess, response) {
    if (isSuccess) {
      //do something
    } else {
      // do something else
    }
  };
  
  // Sends request to server
  a.Fetch.list(requestParam, callback);
  
}

Answer 1

Likely the request that happens in the Fetch call is asynchronous and Safari is not waiting for it to finish before moving on to the next page/closing the tab. If you can make the call synchronous it should work. Keep in mind that synchronous calls are generally discouraged and deprecated in some tools.

This answer related to Jquery has a good explanation of synchronous calls: https://stackoverflow.com/a/11755262/1341437