Learn all about the jQuery function deferred.notify().
Normally, only the creator of a Deferred should call this method; you can prevent other code from changing the Deferred’s state or reporting status by returning a restricted Promise object through deferred.promise().
deferred.notify is called, any progressCallbacks added by
deferred.progress are called. Callbacks are executed in the order they were added. Each callback is passed the
args from the
.notify(). Any calls to
.notify() after a Deferred is resolved or rejected (or any progressCallbacks added after that) are ignored. For more information, see the documentation for Deferred object.