Discovering the bound ASP.NET AJAX event handlers for a specific DOM element

Question

Discovering the bound ASP.NET AJAX event handlers for a specific DOM element

I am currently working on customizing a pre-existing ASP.NET 3.5 AJAX web application, specifically SharePoint 2010. Unfortunately, I do not have the ability to modify the source code.

My task involves adding a click event handler to act as the first event on a Close button. Before doing so, I would like to check the existing event handlers already registered on this button to ensure I do not disrupt any functionality.

While I am still in the process of learning ASP.NET AJAX, I have noticed that the Sys.UI.DomEvent class provides methods for adding and removing event handlers but does not have a built-in way to enumerate them. Fortunately, I am well-versed in jQuery and comfortable with JavaScript debugging in Chrome.

Can someone advise me on how I can identify which events are registered and insert a custom event handler at a specific position?

javascript asp.net dom-events asp.net-ajax

Answer 1

Answer №1

There's a clever little trick that can help you secure your spot at the front of the line (unless someone else is using the same method - which is highly unlikely).

The key is to hijack the click event. This technique is exemplified in this related question: Hijacking onchange event without interfering with original function

All you need to do is redefine the click function to suit your needs, like so:

var myButton = document.getElementById('button1')
var oldClick = myButton.click;

myButton.click = function(evt) {
  //determine your desired actions here. Afterward, call the default click function:
  if (oldClick) oldClick(evt);
}

(although the syntax in the linked question is more advanced, the code above is easier to understand).

Answer 2

There's a clever little trick that can help you secure your spot at the front of the line (unless someone else is using the same method - which is highly unlikely).

The key is to hijack the click event. This technique is exemplified in this related question: Hijacking onchange event without interfering with original function

All you need to do is redefine the click function to suit your needs, like so:

var myButton = document.getElementById('button1')
var oldClick = myButton.click;

myButton.click = function(evt) {
  //determine your desired actions here. Afterward, call the default click function:
  if (oldClick) oldClick(evt);
}

(although the syntax in the linked question is more advanced, the code above is easier to understand).

Discovering the bound ASP.NET AJAX event handlers for a specific DOM element

Answer №1

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