test if event handler is bound to an element in jQuery

Question

Is it possible to determine whether an element has a click handler  or a change handler  or any kind of event handler bound to it using jQuery   Furthermore  is it possible to determine how many click handlers  or whatever kind of event handlers  it has for a given type of event  and what functions are in the event handlers

User · Accepted Answer

You can get this information from the data cache.

For example, log them to the console (firebug, ie8):

console.dir( $('#someElementId').data('events') );

or iterate them:

jQuery.each($('#someElementId').data('events'), function(i, event){

    jQuery.each(event, function(i, handler){

        console.log( handler.toString() );

    });

});

Another way is you can use the following bookmarklet but obviously this does not help at runtime.

User · Answer

With reference to SJG s answer and from W3Schools com      As of jQuery version 1 7  the off   method is the new replacement for the unbind    die   and undelegate   methods  This method brings a lot of consistency to the API  and we recommend that you use this method  as it simplifies the jQuery code base      This gives       someid   off  click   live  click  function         or      someid   off  click   bind  click  function

User · Answer

I think this might have updated with jQuery 1 9    I m finding the this is the only thing that works for me at the moment      data     yourElementID   0   events

User · Answer

I had the same need  amp  quickly patched an existing code to be able to do something like this     if      scroll   hasHandlers  mouseout         could be click  or                   code         It works for event delegation too     if       main   hasHandlers  click    simple-search            It is available here   jquery-handler-toolkit js

User · Answer

I wrote a very tiny plugin called  once  which do that     fn once   function a  b        return this each function               this  off a  on a b                And simply     element  once  click   function

User · Answer

Killing off the binding when it does not exist yet is not the best solution but seems effective enough  The second time you    click    you can know with certainty that it will not create a duplicate binding   I therefore use die   or unbind   like this       someid   die  click   live  click  function         or      someid   unbind  click   bind  click  function         or in recent jQuery versions       someid   off  click   on  click  function

User · Answer

I don t think that the hasEventListener plugin mentioned will handle custom events e g   var obj    id  test      obj  bind  custom   function        alert  custom       trigger  custom     alert   obj  hasEventListener  custom       Also  at least in jQuery 1 5 I think you need to be careful using   target  data  events   because it returns differently for events that have been bound to objects as above    You need to do something like   var events     target  data  events    if typeof events      function       events   events events      I am using this sort of approach and it works but it feels a bit like I am at the mercy of jquery internals and that really I shouldn t be doing it

User · Answer

This works for me      profile1   attr  onclick

User · Answer

This solution is no more supported since jQuery 1 8 as we can read on the blog here        element  data    events      This is now removed in 1 8  but you can still get to the   events data for debugging purposes via    data element   events      Note that this is not a supported public interface  the actual data   structures may change incompatibly from version to version    So  you should unbind rebind it or simply  use a boolean to determine if your event as been attached or not  which is in my opinion the best solution

User · Answer

I wrote a plugin called hasEventListener which exactly does that    http   github com sebastien-p jquery hasEventListener  Hope this helps

User · Answer

For jQuery 1 9   var eventListeners      data     classname   0    events      I needed the  0  array literal

[javascript] test if event handler is bound to an element in jQuery

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