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jQuery find events handlers registered with an object

I need to find which event handlers are registered over an object.

For example:

$("#el").click(function() {...});
$("#el").mouseover(function() {...});

$("#el") has click and mouseover registered.

Is there a function to find out that, and possibly iterate over the event handlers?

If it is not possible on a jQuery object through proper methods, is it possible on a plain DOM object?

unfortunately, now: bugs.jquery.com/ticket/10589
support both jQuery pre and post 1.8: var events = (jQuery._data || jQuery.data)(elem, 'events');
Note that you can use the FF and Chrome dev-tools (the F12) to see these event listeners. See developers.google.com/web/tools/chrome-devtools/debug/… and developer.mozilla.org/en-US/docs/Tools/Page_Inspector/How_to/…

g
gnarf

As of jQuery 1.8, the event data is no longer available from the "public API" for data. Read this jQuery blog post. You should now use this instead:

jQuery._data( elem, "events" );

elem should be an HTML Element, not a jQuery object, or selector.

Please note, that this is an internal, 'private' structure, and shouldn't be modified. Use this for debugging purposes only.

In older versions of jQuery, you might have to use the old method which is:

jQuery( elem ).data( "events" );

but you can still use $._data($(elem).get(0), "events")
blog.jquery.com/2011/11/08/building-a-slimmer-jquery .data(“events”): jQuery stores its event-related data in a data object named (wait for it) events on each element. This is an internal data structure so in 1.8 this will be removed from the user data name space so it won’t conflict with items of the same name. jQuery’s event data can still be accessed via jQuery._data(element, "events") but be aware that this is an internal data structure that is undocumented and should not be modified.
Seamlessly support both options: var events = (jQuery._data || jQuery.data)(elem, 'events');
@CrazyMerlin ok, thanks for that. Now maybe you have a better answer?
it's returning undefined.
N
Nick Craver

You can do it by crawling the events (as of jQuery 1.8+), like this:

$.each($._data($("#id")[0], "events"), function(i, event) {
  // i is the event type, like "click"
  $.each(event, function(j, h) {
    // h.handler is the function being called
  });
});

Here's an example you can play with:

$(function() { $("#el").click(function(){ alert("click"); }); $("#el").mouseover(function(){ alert("mouseover"); }); $.each($._data($("#el")[0], "events"), function(i, event) { output(i); $.each(event, function(j, h) { output("- " + h.handler); }); }); }); function output(text) { $("#output").html(function(i, h) { return h + text + "
"; }); }

Test


Works with 1.4, but not in jQuery 1.8.2.
For jQuery 1.8+, you must use the 'private data' method: jQuery._data( jQuery("#el")[0], "events" ); instead of the 'public data' method: jQuery("#el").data("events"). The events object hasn't actually been stored in .data() for a long time, we trimmed a few bytes of code out by removing this "proxy" from the "public API"
P
PhistucK

For jQuery 1.8+, this will no longer work because the internal data is placed in a different object.

The latest unofficial (but works in previous versions as well, at least in 1.7.2) way of doing it now is - $._data(element, "events")

The underscore ("_") is what makes the difference here. Internally, it is calling $.data(element, name, null, true), the last (fourth) parameter is an internal one ("pvt").


$._data("body", "events") undefined $().jquery; "1.7.1" (tried 1.7.2 and 1.8.1 all the time "undefined")
@Michal - api.jquery.com/jQuery.data says it accepts an element, not a selector.
Now works fine: $._data($("body").get(0), "events") Or even better: $("body").data("events") !
FWIW - Pointing out that it 'internally' calls the other data function with a parameter we specifically don't document probably isn't needed. But yes, jQuery._data( element, "events" ) is the 'correct' way to get this information now.
R
Rui

Shameless plug, but you can use findHandlerJS

To use it you just have to include findHandlersJS (or just copy&paste the raw javascript code to chrome's console window) and specify the event type and a jquery selector for the elements you are interested in.

For your example you could quickly find the event handlers you mentioned by doing

findEventHandlers("click", "#el")
findEventHandlers("mouseover", "#el")

This is what gets returned:

element The actual element where the event handler was registered in

events Array with information about the jquery event handlers for the event type that we are interested in (e.g. click, change, etc) handler Actual event handler method that you can see by right clicking it and selecting Show function definition selector The selector provided for delegated events. It will be empty for direct events. targets List with the elements that this event handler targets. For example, for a delegated event handler that is registered in the document object and targets all buttons in a page, this property will list all buttons in the page. You can hover them and see them highlighted in chrome.

handler Actual event handler method that you can see by right clicking it and selecting Show function definition

selector The selector provided for delegated events. It will be empty for direct events.

targets List with the elements that this event handler targets. For example, for a delegated event handler that is registered in the document object and targets all buttons in a page, this property will list all buttons in the page. You can hover them and see them highlighted in chrome.

You can try it here


A
Anton

I use eventbug plugin to firebug for this purpose.


Thanks, great tip. The extension adds a tab to Firebug ("Events") that shows the events of the page, so you can expore them easily.
Also, Chrome Developer Tools has "Event Listeners" under the "Elements" tab and "Event Listener Breakpoints" under the "Sources" tab.
a
algorhythm

I've combined both solutions from @jps to one function:

jQuery.fn.getEvents = function() {
    if (typeof(jQuery._data) === 'function') {
        return jQuery._data(this.get(0), 'events') || {};
    }

    // jQuery version < 1.7.?
    if (typeof(this.data) === 'function') {
        return this.data('events') || {};
    }

    return {};
};

But beware, this function can only return events that were set using jQuery itself.


T
Tom G

To check for events on an element:

var events = $._data(element, "events")

Note that this will only work with direct event handlers, if you are using $(document).on("event-name", "jq-selector", function() { //logic }), you will want to see the getEvents function at the bottom of this answer

For example:

 var events = $._data(document.getElementById("myElemId"), "events")

or

 var events = $._data($("#myElemId")[0], "events")

Full Example:

<html>
    <head>
        <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js" type="text/javascript"></script>
        <script>
            $(function() {
                $("#textDiv").click(function() {
                    //Event Handling
                });
                var events = $._data(document.getElementById('textDiv'), "events");
                var hasEvents = (events != null);
            });
        </script>
    </head>
    <body>
        <div id="textDiv">Text</div>
    </body>
</html>

A more complete way to check, that includes dynamic listeners, installed with $(document).on

function getEvents(element) {
    var elemEvents = $._data(element, "events");
    var allDocEvnts = $._data(document, "events");
    for(var evntType in allDocEvnts) {
        if(allDocEvnts.hasOwnProperty(evntType)) {
            var evts = allDocEvnts[evntType];
            for(var i = 0; i < evts.length; i++) {
                if($(element).is(evts[i].selector)) {
                    if(elemEvents == null) {
                        elemEvents = {};
                    }
                    if(!elemEvents.hasOwnProperty(evntType)) {
                        elemEvents[evntType] = [];
                    }
                    elemEvents[evntType].push(evts[i]);
                }
            }
        }
    }
    return elemEvents;
}

Example usage:

getEvents($('#myElemId')[0])

This getEvents method is overally great, but the thing is, it gives duplicate entries in IE11 (I know, IE again, but corporate needs it...). EDIT: $._data contains duplicate events for element, even though on FF it doesn't contain any... Weird IE world. But it's important to watch out for this possibility of having duplicate events.
Oh, Tom, it's actually your code that's multiplying events with each execution of this method. Not good.
o
oligofren

As of 1.9 there is no documented way to retrieve the events, other than to use the Migrate plugin to restore the old behavior. You could use the _.data() method as jps mentions, but that is an internal method. So just do the right thing and use the Migrate plugin if you need this functionality.

From the jQuery documentation on .data("events")

Prior to 1.9, .data("events") could be used to retrieve jQuery's undocumented internal event data structure for an element if no other code had defined a data element with the name "events". This special case has been removed in 1.9. There is no public interface to retrieve this internal data structure, and it remains undocumented. However, the jQuery Migrate plugin restores this behavior for code that depends upon it.


The accepted answer also clearly shows the new, correct way to get it for recent versions: jQuery._data( elem, "events" );...
A private, undocumented way will never be a correct way. The correct way - meaning documented, public, and intended - is to use the Migrate plugin.
You seem to misunderstand the point of the Migrate plugin. jQuery removed deprecated features, and the Migrate plugin is to help migrate developer's code to the newer versions so that they can immediately take advantage of new features and improvements, but not lose functionality. It's meant to help the coder see what they need to do in order to start properly using new versions of jQuery. You shouldn't use it in production to restore features. Also, many things aren't documented and up to date in jQuery documentation - they've pointed it out before, so that's not a reason
Also, if it's included as a suggestion in the jQuery blog, I'd use it: blog.jquery.com/2012/08/09/jquery-1-8-released
Your reasoning on the Migrate plugin seems reasonable. OK if I delete my answer?
E
Erutan409

I created a custom jQuery selector that checks against both jQuery's cache of assigned event handlers as well as elements that use the native method for adding them:

(function($){

    $.find.selectors[":"].event = function(el, pos, match) {

        var search = (function(str){
            if (str.substring(0,2) === "on") {str = str.substring(2);}
            return str;
        })(String(match[3]).trim().toLowerCase());

        if (search) {
            var events = $._data(el, "events");
            return ((events && events.hasOwnProperty(search)) || el["on"+search]);
        }

        return false;

    };

})(jQuery);

Example:

$(":event(click)")

This will return elements that have a click handler attached to them.


J
Jesan Fafon

In a modern browser with ECMAScript 5.1 / Array.prototype.map, you can also use

jQuery._data(DOCUMENTELEMENT,'events')["EVENT_NAME"].map(function(elem){return elem.handler;});

in your browser console, which will print the source of the handlers, comma delimited. Useful for glancing at what all is running on a particular event.


jQuery._data('ct100_ContentPlaceHolder1_lcsSection','events')["EVENT_NAME"].map(function(elem){return elem.handler;}); Uncaught TypeError: Cannot read property 'EVENT_NAME' of undefined at <anonymous>:1:62
'ct100_ContentPlaceHolder1_lcsSection' is a string, not a DOM Element.
R
R. Oosterholt

Events can be retrieved using:

jQuery(elem).data('events');

or jQuery 1.8+:

jQuery._data(elem, 'events');

Note: Events bounded using $('selector').live('event', handler) can be retrieved using:

jQuery(document).data('events')

jQuery(document).data('events') gives me undefined
D
Dominik Szymański

jQuery is not letting you just simply access the events for a given element. You can access them using undocumented internal method

$._data(element, "events")

But it still won't give you all the events, to be precise won't show you events assigned with

$([selector|element]).on()

These events are stored inside document, so you can fetch them by browsing through

$._data(document, "events")

but that is hard work, as there are events for whole webpage.

Tom G above created function that filters document for only events of given element and merges output of both methods, but it had a flaw of duplicating events in the output (and effectively on the element's jQuery internal event list messing with your application). I fixed that flaw and you can find the code below. Just paste it into your dev console or into your app code and execute it when needed to get nice list of all events for given element.

What is important to notice, element is actually HTMLElement, not jQuery object.

function getEvents(element) {
    var elemEvents = $._data(element, "events");
    var allDocEvnts = $._data(document, "events");
    function equalEvents(evt1, evt2)
    {
        return evt1.guid === evt2.guid;
    }

    for(var evntType in allDocEvnts) {
        if(allDocEvnts.hasOwnProperty(evntType)) {
            var evts = allDocEvnts[evntType];
            for(var i = 0; i < evts.length; i++) {
                if($(element).is(evts[i].selector)) {
                    if(elemEvents == null) {
                        elemEvents = {};
                    }
                    if(!elemEvents.hasOwnProperty(evntType)) {
                        elemEvents[evntType] = [];
                    }
                    if(!elemEvents[evntType].some(function(evt) { return equalEvents(evt, evts[i]); })) {
                        elemEvents[evntType].push(evts[i]);
                    }
                }
            }
        }
    }
    return elemEvents;
}

p
pid

I have to say many of the answers are interesting, but recently I had a similar problem and the solution was extremely simple by going the DOM way. It is different because you don't iterate but aim directly at the event you need, but below I'll give a more general answer.

I had an image in a row:

<table>
  <td><tr><img class="folder" /></tr><tr>...</tr></td>
</table>

And that image had a click event handler attached to it:

imageNode.click(function () { ... });

My intention was to expand the clickable area to the whole row, so I first got all images and relative rows:

tableNode.find("img.folder").each(function () {
  var tr;

  tr = $(this).closest("tr");
  // <-- actual answer
});

Now in the actual anwer line I just did as follows, giving an answer to the original question:

tr.click(this.onclick);

So I fetched the event handler directly from the DOM element and put it into the jQuery click event handler. Works like a charm.

Now, to the general case. In the old pre-jQuery days you could get all events attached to an object with two simple yet powerful functions gifted to us mortals by Douglas Crockford:

function walkTheDOM(node, func)
{
  func(node);
  node = node.firstChild;
  while (node)
  {
    walkTheDOM(node, func);
    node = node.nextSibling;
  }
}

function purgeEventHandlers(node)
{
  walkTheDOM(node, function (n) {
    var f;

    for (f in n)
    {
      if (typeof n[f] === "function")
      {
        n[f] = null;
      }
    }
  });
}

M
Marquinho Peli
t
tempranova

Another way to do it is to just use jQuery to grab the element, then go through actual Javascript to get and set and play with the event handlers. For instance:

var oldEventHandler = $('#element')[0].onclick;
// Remove event handler
$('#element')[0].onclick = null;
// Switch it back
$('#element')[0].onclick = oldEventHandler;

I think that jQuery does event handling optimization which I think is circumvented by your code here.
Thanks, yeah I had a feeling this was hacky - any good link to learn more about that optimization?
M
Marek Lisý

I combined some of the answers above and created this crazy looking but functional script that lists hopefully most of the event listeners on the given element. Feel free to optimize it here.

var element = $("#some-element"); // sample event handlers element.on("mouseover", function () { alert("foo"); }); $(".parent-element").on("mousedown", "span", function () { alert("bar"); }); $(document).on("click", "span", function () { alert("xyz"); }); var collection = element.parents() .add(element) .add($(document)); collection.each(function() { var currentEl = $(this) ? $(this) : $(document); var tagName = $(this)[0].tagName ? $(this)[0].tagName : "DOCUMENT"; var events = $._data($(this)[0], "events"); var isItself = $(this)[0] === element[0] if (!events) return; $.each(events, function(i, event) { if (!event) return; $.each(event, function(j, h) { var found = false; if (h.selector && h.selector.length > 0) { currentEl.find(h.selector).each(function () { if ($(this)[0] === element[0]) { found = true; } }); } else if (!h.selector && isItself) { found = true; } if (found) { console.log("################ " + tagName); console.log("event: " + i); console.log("selector: '" + h.selector + "'"); console.log(h.handler); } }); }); });