The .ajaxStart() method registers a handler to be called when the first Ajax request begins.
Whenever an Ajax request is about to be sent, jQuery checks whether there are any other outstanding Ajax requests. If none are in progress, jQuery triggers the ajaxStart event. Any and all handlers that have been registered with the ajaxStart() method are executed at this time.
This method has the form:
|function()||Specifies the function to run when the ajaxStart event is triggered|
This form returns a jQuery object.