Sys.WebForms.PageLoadedEventArgs panelsUpdated Property
Gets an array of HTML <div> elements that represent UpdatePanel controls that were updated when the DOM was updated during the last asynchronous postback.
To get or set property values for client API properties, you must call property accessor methods that are named with the get_ and set_ prefixes. For example, to get or set a value for a property such as cancel, you call the get_cancel or set_cancel methods.
var arr = eventArgs.get_panelsUpdated()
An array of <div> elements that were updated during the DOM manipulation that was the result of the last asynchronous postback. If no elements were created, the property returns null.
If an UpdatePanel control is updated as a result of a partial-page update, the array referenced in the panelsUpdated property of the PageLoadedEventArgs class contains a reference to the corresponding <div> element. The pageLoaded event of the Sys.WebForms.PageRequestManager class uses a PageLoadedEventArgs object to return its event data.