jQuery ajax async: false causes a strange warning?

Question

In my JS App, i have many Ajax calls with async: false. I am using latest Chrome browser and in my console below warning appears recently.

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Answer 1

JavaScript runs exclusively on the UI thread so a synchronous AJAX call will freeze the browser completely, until the server replies.

It's considered a bad pratice in UX Design for web applications and major browsers are deprecating this feature in favor of asynchronous requests with a callback.

You may not worry about the message now. It's not a bug but I strongly recommend you to start rewriting it because when a feature is marked as deprecated it means a warn that they can remove this feature anytime in the future.

It's also deprecated from jQuery 1.8+

As of jQuery 1.8, the use of async: false with jqXHR ($.Deferred) is deprecated; you must use the success/error/complete callback options instead of the corresponding methods of the jqXHR object such as jqXHR.done() or the deprecated jqXHR.success()

The recomended way:

var request = $.ajax({
  url: "script.php",
  data: { id : menuId },
  dataType: "application/json"
});

request.done(function(data) {
   // Executed in case of success
});

request.fail(function( jqXHR, textStatus ) {
  // Executed in case of error
});