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javascript how to determine what is cancelling an event

I have jquery, bootstrap included in a page I'm writing. It's a complex page. The problem I'm having is with Internet Explorer not seeing mousedown event. Chrome and FF both see the event just fine but not IE.
I wrote a test page with the event and it worked just fine in IE. So my question is...
Is there a way through the developer tools to determine what is cancelling an event?
I have a suspicion that one of the many .js files I've included is cancelling the mousedown event and IE isn't seeing it anymore. Chrome and FF does though. So I'm not 100% that it's being cancelled but it's my only guess I can come up with.
Code is really irrelevant since it's all of jquery and bootstrap. However, I am playing with divs that are draggable and resizeable. That's why I need to use jquery. The bootstrap is used because I also have a wysiwyg editor on the page.
Please don't recommend click. I need mousedown. When the mouse is down the border around the draggable and resizeable div turns red and I have some code that selects that div to capture top, left, width, and height as it's being moved and resized.
If click was selected as the event, the user would have to click the div box first then click and hold to move it. That's not a user friendly interface.
Any help is greatly appreciated.

What do you exactly mean as cancel, .preventDefault() or .stopPropagation? If we are talking about preventDefault - you should still be able to add event listener to parent container and then see your event object - it might have some data to traceback. Alternative would to override jQuery .on method and see who actually subscribes to the event.
After little more thinking - add another listener BEFORE the malicious one, to do that insert document-ready handler with event binding right after jquery loading code. In your new mousedown handler try to override problematic method of the event.
UPDATE:
you should try to check all events attached to your element one by one. To do that - check this post jQuery find events handlers registered with an object
In short - try using jQuery._data( elem, "events" ); to see attached event listeners and inspect their code in your code base. After you find the reason it will be much easier to reach the desired functionality. Before that it is just a guesswork.

How to generally find out what javascript controls the behavior of a general element on a webpage?

Look at this fiddle http://jsfiddle.net/52VtD/2635/
Inside it you can see one tooltip working.
Suppose we weren't looking at a fiddle though, and couldn't see the javascript source, but we wanted to know what was controlling this tooltip behavior?
The answer is
$("#tooltip1").tooltip();
So how do we find that answer using chrome or firefox inspector, or some other debug/browser inspector stuff? Preferably it would be quick, as opposed to downloading all .js files and prettifying them in an IDE and then manually searching.

There is no quick answer to this. You pretty much have to analyze a specific situation and see what clues you can then go look for.
In this particular case, you're going to suspect that there's an event listener attached to the #tooltip object. You can first look in the Chrome debugger for event listeners. Right click on the button, select Inspect Element, click on the Event Listeners tab and then look at the event listeners. In this particular case, you will see a bunch of them for that object. What you want is mouseout and mouseover. But, when you see where the event listeners are attached, it just take you to the internals of jQuery. This is a challenge with a library because it's the library that actually attached the event as part of some higher level API that the developer used.
So, now you know that jQuery was used to attach these events. You need to figure out where in the code these events where attached. To do this, you need to develop a theory about how the developer identified this particular object in jQuery. Since there is no particular structure to this simple document, the likely way that the developer found this particular object is with a "#tooltip" selector passed to some jQuery function. So, at this point, I would search all the JS in the page for "#tooltip" and see what you find.
While still in the Chrome debugger, you can hit Ctrl+F and enter #tooltip. Then, hit enter several times as it takes you to different uses of that and the third time, it will take you to:
$("#tooltip1").tooltip();
And, you will have your answer. Obviously, every problem like this is a bit different and it takes some detective work and searching to figure out what clues to search for in the Javascript. Some cases are much harder than others.

In *Chrome** you can bring up the developer tools buy clicking f12 and on the right you should see a tab titled "Event Listeners". Here you should see the event listeners for the page your are on.
This should have all the Event Listener info you could ever want :)

jQuery & Chrome - Finding Button Hooks

Using Chrome's developer tools I am trying to determine what jQuery function is hooking an input button on the page for debugging purposes. I usually just keep searching until I find it, but I figured I'd ask this time.
Is there a way to find a jQuery button hook for a specific button in Chrome? I've tried looking through the Event Listener Breakpoints, but can never seem to find the right thing to pause it.
Basically, I need to know what jQuery / Javascript is being executed after the button is clicked.
The hooks are implemented in the application like so:
$('.button_class').click(function (){
$('#button_id').click(function(){
etc...

try this :
$(yourbutton).data('events');

Depending on the number of events/timers on the page this doesn't always work. But you can try "pausing" before clicking the button you want to debug in the JavaScript debug window. That way the debugger will pause on the next line that executes. The thing that occasionally prevents you from using that is if there is a "hover" or mouse move/in/out event tied on an element you have to pass over to get to the button (including the button itself). In that case I just remove those events (if I can) until I get the one I want. The event listener breakpoints would be more ideal but they're sometimes difficult when using jQuery or another library, I've actually put in a feature request to the Chrome Dev Tools team to address this very issue. (allowing you to specify what files are "yours" and only "breaking" in those specific files)
good luck -ck

Using Chrome, how to find to which events are bound to an element

Lets suppose I've a link on my page:
Click Here
I don't know anything else, but when I click on the link, an alert("bar") is displayed.
So I know that somewhere, some code is getting bound to #foo.
How can I find the code that is binding the alert("bar") to the click event?
I'm looking for a solution with Chrome.
Ps.: The example is fictive, so I'm not looking for solution like: "Use XXXXXX and search the whole project for "alert(\"bar\")". I want a real debugging/tracing solution.

Using Chrome 15.0.865.0 dev. There's an "Event Listeners" section on the Elements panel:
And an "Event Listeners Breakpoints" on the Scripts panel. Use a Mouse -> click breakpoint and then "step into next function call" while keeping an eye on the call stack to see what userland function handles the event. Ideally, you'd replace the minified version of jQuery with an unminified one so that you don't have to step in all the time, and use step over when possible.

You can also use Chrome's inspector to find attached events another way, as follows:
Right click on the element to inspect, or find it in the 'Elements' pane.
Then in the 'Event Listeners' tab/pane, expand the event (eg 'click')
Expand the various sub-nodes to find the one you want, and then look for where the 'handler' sub-node is.
Right click the word 'function', and then click 'Show function definition'
This will take you to where the handler was defined, as demonstrated in the following image, and explained by Paul Irish here: https://groups.google.com/forum/#!topic/google-chrome-developer-tools/NTcIS15uigA

Give it a try to the jQuery Audit extension (https://chrome.google.com/webstore/detail/jquery-audit/dhhnpbajdcgdmbbcoakfhmfgmemlncjg), after installing follow these steps:
Inspect the element
On the new 'jQuery Audit' tab expand the Events property
Choose for the Event you need
From the handler property, right click over function and select 'Show function definition'
You will now see the Event binding code
Click on the 'Pretty print' button for a more readable view of the code

(Latest as of 2022) For version Chrome Version Version 99:
Select the element you want to inspect
Choose the Event Listeners tab
Make sure to check the Framework listeners to show the real javascript file instead of the jquery function.

Edit: in lieu of my own answer, this one is quite excellent: How to debug JavaScript/jQuery event bindings with Firebug (or similar tool)
Google Chromes developer tools has a search function built into the scripts section
If you are unfamiliar with this tool: (just in case)
right click anywhere on a page (in chrome)
click 'Inspect Element'
click the 'Scripts' tab
Search bar in the top right
Doing a quick search for the #ID should take you to the binding function eventually.
Ex: searching for #foo would take you to
$('#foo').click(function(){ alert('bar'); })

2018 Update - Might be helpful for future readers:
I am not sure when this was originally introduced in Chrome. But another (easy) way this can be done now in Chrome is via console commands.
For example: (in chrome console type)
getEventListeners($0)
Whereas $0 is the selected element in the DOM.
https://developers.google.com/web/tools/chrome-devtools/console/command-line-reference#0_-_4

findEventHandlers is a jquery plugin, the raw code is here: https://raw.githubusercontent.com/ruidfigueiredo/findHandlersJS/master/findEventHandlers.js
Steps
Paste the raw code directely into chrome's console(note:must have jquery loaded already)
Use the following function call: findEventHandlers(eventType, selector);
to find the corresponding's selector specified element's eventType handler.
Example:
findEventHandlers("click", "#clickThis");
Then if any, the available event handler will show bellow, you need to expand to find the handler, right click the function and select show function definition
See: https://blinkingcaret.wordpress.com/2014/01/17/quickly-finding-and-debugging-jquery-event-handlers/

For Chrome Version 52.0.2743.116:
In Chrome's Developer Tools, bring up the 'Search' panel by hitting Ctrl+Shift+F.
Type in the name of the element you're trying to find.
Results for binded elements should appear in the panel and state the file they're located in.

Track events using Chrome javascript debugger

I don't have a specific use case here, but occasionally I have been either helping out someone on SO or seen a cool javascript effect on a website and been curious about the code that drives it. However, the event that drives the code may not be immediately obvious. If I can't find the event handler then it can be really hard to find the js responsible for the effects I am interested in. Is there a quick way in the debugger to identify the events attached to an element and to drop a break point in when it fires?
So for example an event may exist on a structure something like so
<div>
<ul>
<li><span><img /></span></li>
</ul>
</div>
Now I don't know if the event is bound to the img, span, li, ul or div itself. Chrome has the Event Listeners area, but I feel like it doesn't always contain events. Anything you guys do that allows you to quickly find the event and drop a break point into it?

yes there is!
find the element that is being reloaded and right click,
choose inspect from context menu,
then right click the html of the element (in the bottom firebugish pane),
in the context menu there are options to:
break on subtree modifications
break on attributes modifications
break on node removal
Article on awesome new dev features in chrome:
http://elijahmanor.com/7-chrome-tips-developers-designers-may-not-know/

If you have access to the .js, just add "debugger;" on its own line. Whenever Chrome (or FF) hits that, it'll trigger the debugger and let you walk through. Esp useful if you have some general idea which code will trigger the event. See http://beerpla.net/2009/12/17/how-to-make-firebugs-javascript-debugger-break-inside-dynamic-javascript-using-the-debugger-keyword-ie-chrome-too/ for more.

Right click on the element in chrome dev tools, and click on 'break on' , then you would see multiple selections such as sub tree modifications. Or you could also go to chrome//:tracing