Develop Reference

jQuery - Register / unregister listener for element "document"

I'll try to explain my problem. I'm using mouseup event listener so I can check whenever a click is performed and the target is not the desired element. This is the code I'm using:
function clickOutListener(element, callbackFunction){
$(document).mouseup(function(e){
if(!$(element).is(e.target) && $(element).has(e.target).length === 0) callbackFunction.call(this, null);
});
}
As you can see, the event listener is bound to the global document element and the way to unbind the listener would be:
$(document).off("mouseup");
Here comes what I need to achieve. If I unbind mouseup listener it will affect the other elements which use this listener (dropdowns and other features). I must guess that everytime I'm registering a listener it's not overriding the previous defined listener but adding the defined target function.
How can I access the different defined target functions for the same listeners?
$(document).mouseup(funct1);
$(document).mouseup(funct2);
$(document).mouseup(funct3);
How would you unregister the registered listener just for "funct2"?
Thank you in advance.

You can namespace your events when using the .on() syntax.
$(document).on('mouseup.myNamespace', function(e){ ... }
This allows you to remove events by namespace whilst leaving others in place.
$(document).off('mouseup.myNamespace');

Jquery off() for a specific element

I have a table where i have bound all my elements with class="shift" to a click function.
Now, because I also need to use another click event on part of the element, I would like to unbind the click event on element when the mouse enters the element and rebind when i leaves (meant for some touch events and whatnot)
Now, I bind like this
$("table").on("touchstart mousedown",".shift", function(e){ ... })
But when i try to unbind on a specific element, say it has a class="selected" added to distinguish the current element i use:
$("table").off("touchstart mousedown",".shift.selected")
which does not work....
I can remove all the handlers at once, but it would be wasteful to remove all the handlers and reinsert them as soon as the mouse leaves.
So, is there a way to remove the handler on a single element after the event is bound to all current and future elements?
Thanks in advance!

You don't need to unbind the click event on the element when the mouse enters. I know, the element click event will trigger when you click an inner element with the click event bound, right ? you can stop that:
The click handler of the inner element must look like this:
$("some inner element").click(function(event) {
//That's what are you looking for ;)
event.stopPropagation();
//You code here
});
event.stopPropagation() will prevent the event from bubbling up the DOM tree, preventing any parent handlers from being notified of the event.

Delegated events don't work in combination with :not() selector

I want to do something on all clicks except on a certain element.
I've created a very simple example which demonstrates the issue: http://jsfiddle.net/nhe6wk77/.
My code:
$('body').on('click', ':not(a)', function () {
// do stuff
});
I'd expect all click to on <a> to be ignored, but this is not the case.
Am I doing something wrong or is this a bug on jQuery's side?

There's a lot going on in that code that's not obvious. Most importantly, the click event is actually attached to the body element. Since that element isn't an anchor, you'll always get the alert. (Event delegation works because the click event bubbles up from the a through all its ancestors, including body, until it reaches document.)
What you want to do is check the event.target. That will tell you the element that was actually clicked on, but the actual click event is still bound to the body element:
$('body').on('click', function (e) { // e = event object
if ($(e.target).is(':not(a)')) {
alert('got a click');
}
});
http://jsfiddle.net/y3kx19z7/

No this is not a bug but rather intended behaviour.
The event bubbles all the way up. By clicking the a node, you are still triggering it's parents event from the div node.
Read more about event bubbling in the W3C DOM Specification. Just search for "bubble".
You need to stop the event propagation of the a nodes. i.e.:
$('body').on('click', ':not(a)', function () {
// do something effectively
alert('you should not see me when clicking a link');
});
$("a").click(function( event ) {
// do nothing effectively, but stop event bubbling
event.stopPropagation();
});
JSFiddle: http://jsfiddle.net/nhe6wk77/6/

It's working as intended, here's why!
Use of the :not() selector is honored in delegated events, but it's an uncommon practice because of how events bubble up the DOM tree potentially triggering the handler multiple times along the way.
The jQuery API Documentation states that:
jQuery bubbles the event from the event target up to the element where the handler is attached (i.e., innermost to outermost element) and runs the handler for any elements along that path matching the selector.
Notice the phrase "and runs the handler for any elements along that path matching the selector".
In your example, jQuery is accurately not running the handler on the a element, but as the event bubbles up the tree, it runs the handler for any element that matches :not(a), which is every other element in the path.
Here is a clear example showing how this works: http://jsfiddle.net/gfullam/5mug7p2m/
$('body').on('click', ':not(a)', function (e) {
alert($(this).text());
});
<div class="outer">
<div class="inner">
Click once, trigger twice
</div>
</div>
<div class="outer">
<div class="inner">
<button type="button">Click once, trigger thrice</button>
</div>
</div>
Clicking on the link in the first block of nested divs, will start the event bubbling, but the clicked a element — a.k.a. the event target — doesn't trigger the handler because it doesn't match the :not(a) selector.
But as the event bubbles up through the DOM, each of its parents — a.k.a the event currentTarget — triggers the handler because they do match the :not(a) selector, causing the handler to run twice. Multiple triggering is something to be aware of since it may not be a desired result.
Likewise, clicking on the button in the second block of nested divs, will start the event bubbling, but this time the event target does match the :not(a) selector, so it triggers the handler immediately. Then as the event bubbles up, each of its parents matching the selector triggers the handler, too, causing the handler to run three times.
As others have suggested, you need to either bind an alternate handler that stops propagation on a click events or check the event target against the :not(a) selector inside your handler instead of the delegated selector.

$("body").click(function(e) {
if($(e.target).is('a')){
e.preventDefault();
return;
}
alert("woohoo!");
});
check the target of the click. this way you dont need to bind another event.
updated fiddle

Add on load event for img elements now and in future?

I want to add a load event on an image that would affect that image even when that image is added to the document after the page's initial load. For a click event I would do someting like this:
$(document).on('click', '.elem', function(e) {
// do stuff
});
When I try something similar with the load event, however, it does not to work. This is what I have tried:
$(document).on('load', '.image', function() {
// do stuff
});
This event is simply never triggered. Does anyone know what I may be doing wrong, or how to achieve this?

This answer is incorrect. It's possible to do this using the capture phase, see Dhia Louhichi's answer. I'll delete this answer when I can (i.e.., once it's no longer the accepted answer).
By their nature, delegated handlers only work for events that bubble. Not all do, and load is one of the ones that doesn't. The jQuery documentation even highlights this:
In all browsers, the load, scroll, and error events (e.g., on an element) do not bubble.
You'll have to add the load handlers to the images when you add them.
What I mean by "delegated handlers only work for events that bubble":
Events that bubble work like this (in the "bubbling" phase, which is the phase you normally work with): The event is fired on the element where it originates, and then on that element's parent, then that element's parent, etc. until it gets to the document element (html). This diagram from the DOM3 events spec may help make this clearer:
Using a delegated handler (the kind you're using in your question) relies on bubbling. Consider this HTML:
<div id="container">
<div class="content">xxxx</div>
<div class="content">xxxx</div>
<div class="content">xxxx</div>
</div>
If you do $("#container").on("click", ".content", ...) you're not hooking the event on the "content" divs, even though jQuery will make it seem a bit like you are. You're hooking the event on the "container" div. When the event bubbles down to the container div, jQuery looks at where it started and sees whether it passed through any "content" divs during its bubbling. If it did, jQuery calls your handler as though (mostly) you'd hooked the event on the "content" div. That's why delegated handlers work when you add elements later; the event isn't hooked on the element, but on the container.
So that's why it won't work for load: load doesn't bubble, so even though it fires on the img elements you add, it doesn't bubble to the parent and so on, and so you never see it. To see it, you have to hook it on the specific element, not an ancestor of it.

This code shows handling the load event for img elements created in the future, without explicitly adding a listener/handler to them, by using the capture phase of the event process on document.body (also works when attached to document, but not window because of backward compatibility issues):
document.body.addEventListener(
"load",
function (event) {
var elm = event.target;
if (elm.nodeName.toLowerCase() === 'img') {
console.log("Loaded: " + event.target.src);
}
},
true // Capture phase
);
Live Example:
document.body.addEventListener(
"load",
function (event) {
var elm = event.target;
if (elm.nodeName.toLowerCase() === 'img') {
console.log("Loaded: " + event.target.src);
}
},
true // Capture phase
);
// Brief wait, then add an image
setTimeout(function() {
document.body.insertAdjacentHTML(
"beforeend",
"<img src='https://via.placeholder.com/150/202080?text=Some+Image'>"
);
}, 400);
This is tested and works in at least the following:
IE9+
Chrome and other Chromium-based browsers (Opera, Edge, Vivaldi, ...)
Firefox
iOS Safari
The behavior is also documented. In fact, coincidentally the specification gives this example mentioning load by name (scroll down slightly from that link):
EXAMPLE 5
The following is one way to interpret the above tables: the load event will trigger event listeners attached on Element nodes for that event and on the capture and target phases. This event is not cancelable. If an event listener for the load event is attached to a node other than Window, Document, or Element nodes, or if it is attached to the bubbling phase only, this event listener would not be triggered.
That's saying load will be fired in the capture and target phases, but not the bubbling phase (since the event doesn't bubble).
By default, when you use addEventListener, the handler is attached for the target phase of the element you call addEventListener on and the bubbling phase for any element within that element. If you add the third argument with the value true, though, it attaches the handler for the target phase of the element you call addEventListener on (as before) and the capture phase for any element within that element. So the code above will handle load for document.body during the target phase (except document.body doesn't fire load) and also handle load for the capture phase of any element within document.body.
More about event flows in the specification, including this handy diagram:

JavaScript listen for all focus/blur events

So I'd like some JavaScript which listens for all potential focus/blur events on the page. I can do this for click events quite easily:
document.addEventListener('click', function (e) { console.log('click!') })
Any time any element is clicked, the event will trigger, even if the node was inserted after the event listener was added.
I'd like to do the same for focus events, but they are only triggered on individual elements, and never bubble up to the document.
How can I accomplish this? Is the only way to walk the DOM every few seconds and re-listen in case a new input element has been added?

You can use the focusin and focusout events which bubbles up.
document.addEventListener('focusin', function(e) { console.log('focusin!')})
Demo: Fiddle