Is there anything wrong that can happen if I bind a null selector using on? It would simplify my code and allow me to chain a few things if I didn't have to explicitly check if the selector is null myself.
Any performance, security, or memory-leak implications if I do this a dozen times on my page?
$(document.body).on('click', null, function () { ... }
If you plan on dynamically adding elements, there is nothing wrong by binding on a higher element using the .on() method.
Keep in mind though you have to specify a selector that will ultimately define the dynamically added elements.
The code below will fire when a label is clicked.
$(document).on('click', 'label', function(e) {
alert('dynamically added label clicked');
});
This code will fire when any element is clicked.
$(document).on('click', null, function (e) {
alert('fired regardless what element you clicked');
});
From the jQuery docs:
A selector string to filter the descendants of the selected elements
that will call the handler. If the selector is null or omitted, the
handler is always called when it reaches the selected element.
If your problem is that the elements that raise the click event are dynamically added you can still use a direct event handler on body and catch those events.
The delegated event handler gives you the opportunity to filter out some of those click events, but it seems that's not the case since you are setting the selector to null.
For example, if you have a div and add buttons inside and add an event handler to the click event on the div you'll catch all the click events from all the buttons, even the ones added dynamically.
<div>
<input type="button" value="add button" id="buttonAddMore"/>
<span id="whatClicked"></span>
</div>
$('div').on("click", function(event){
$('#whatClicked').text("the id of the clicked element inside the div is: " + event.target.id);
});
This fiddle demonstrates this.
The delegated events have other subtleties, such as, they won't respond to events raised in the elements they are registered in, in this example that would be a click on the div, and that might be important.
Either way if you look at how the events are registered, in your case you can have a look by calling in the console $._data(document.body, "events") and have a look at the click event handler with your method and registered using the shorthand version (i.e. .click or on("click", function() {...})) you'll see that they produce the same object, except for the selector being null (.on("click", null...) in one case and undefined in the other (.click)
Related
I've attached delegated event handlers to a number of elements on the page using a single selector. As the events are triggered for individual elements, I'd like to turn off only that element's event handler based on some conditional logic. That means I won't necessarily want to disable the event on the very first click. But I can't figure out how to do it without turning off all of them.
HTML:
<button>One</button>
<button>Two</button>
<button>Three</button>
JS:
$(document).on('click', 'button', function(ev) {
// doesn't work because argument needs to be a string
$(document).off('click', $(ev.target));
// doesn't do what I want b/c turns off events on all buttons, not just this one
$(document).off('click', 'button');
// doesn't work because event is on document, not button
$(ev.target).off('click');
});
jQuery's off documentation says I need to provide a string as the second argument, not a jQuery object ($(ev.target)), but if I provide a string, there's no value that refers only to the item clicked.
From jQuery's off documentation:
To remove specific delegated event handlers, provide a selector
argument. The selector string must exactly match the one passed to
.on() when the event handler was attached. To remove all delegated
events from an element without removing non-delegated events, use the
special value "**".
So how do I turn off a delegated event handler for a specific element?
Here's a JSFiddle of the code above
UPDATE: Added a few examples of options that don't work, based on initial answers provided.
After having read thru on the web, the answer is you can't! You can either remove all or none. A workaround could be something like the following.
$(document).on('click', '.btn', function (ev) {
alert('pressed');
$(this).removeClass("btn");
});
Demo#Fiddle
Sample HTML:
<button class="btn">One</button>
<button class="btn">Two</button>
<button class="btn">Three</button>
In addition to what lshettyl said (the current top post) - an additional work around is to bind a new event listener directly to the element that you're trying to remove the listener and call stopPropagation() therein.
What this will do is prevent the event from traveling up the DOM and reaching the event handler that is initially bound to the document. Also this will allow you to keep some functionality on the button click, such as an alert to the user that this button has already been clicked - or something to that effect.
$(document).on('click', 'button', function(ev) {
// Your logic to occur on button click
// Prevent further click on just this button
$(this).click(function(event) {
event.stopPropagation();
}):
});
Question: Do you have to use the delegated events? LIke LShetty said, it is not possible to remove a delegated event for a single element. You either remove the entire event delegation, or leave it. You could try using a different selector instead like in this example
$('button').on('click', function(ev) {
$('#output').append('Clicked! ');
$(this).off('click');
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<button>One</button>
<button>Two</button>
<button>Three</button>
<div id="output"></div>
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
I need some help with the callbacks. For some reason, they don't work really well.
I'm making a game with jQuery. I have a <div id='button'></div> for all the buttons that are going to be in the game. The game is going to have two buttons that make actions, and a question on top of it. The question is controlled by a <h3 id='text'></h3>. What I want to know, is that for some reason I can't set callback functions to the button's ID's. In example,
I'd have the yes or no, that have their own id's set through jQuery like this:
$('#button').html('<button id='yes'>Yes</button><button id='no'></button>');
But for some reason, I would be able to set this:
$('yes').click(function(){
//function I would want
});
Of course, that's not what my code has, that was just an example. Here's the real code:
$(document).ready(function(){
$('#main,#batman,#car,#cop,#hobo,#knife,#gangfight,#ganggun,#gangknife,#blood,#hr').hide(-100);
var hr=$('#hr');
var main=$('#main');
var batman=$('#batman');
var car=$('#car');
var hobo=$('#hobo');
var cop=$('#cop');
var knife=$('#knife');
var gangfight=$('#gangfight');
var ganggun=$('#ganggun');
var gangknife=$('#gangknife');
var blood=$('#blood');
var text=$('#text');
var button=$('#button');
$('#start').html('Are you ready to play?');
$('#button').html('<button id="yes">Yes</button><button id="no">No</button>');
$('#yes').click(function(){
$('#yes,#no').hide(function(){
$('#start').hide();
main.fadeIn(-100);
hr.fadeIn(-100,function(){
text.delay(1000).html("You were just wandering around in the streets of new york, when suddenly.. You see batman!! You've never really liked him, what do you do?")
button.html('<button id="fight">Fight</button><button id="leave">Leave</button>',function(){
batman.fadeIn(1000);
$('fight').click(function(){
});
$('leave').click(function(){
text.fadeOut(function(){
text.text('Good call. As you leave, you encounter a hobo. What do you do?');
});
});
});
});
});
});
$('#no').click(function(){
$('#yes,#no').hide();
$('#start').text('Oh, okay then. Come back later!');
});
});
I'm just wondering.. How can I set callback functions to the 'fight' and 'leave'.
If you're wondering why there's all these variables at the start, those are just the images and characters.
You can't set a click handler on an element that doesn't exist. What you should do is use .on to bind a element further up the tree. Something like:
$("#someparentelement").on("click", "#yes", function() {
// your code
});
Which version of jQuery are you using? You should probably use jQuery.on() in this situation since your click handler code probably gets executed before the button is actually available in the DOM.
$("#button").on("click", "#yes", function (event) {
// Your yes-button logic comes here.
});
For more details and possibilities, read about the .on(events [, selector ] [, data ], handler(eventObject)) method in the jQuery documentation:
If selector is omitted or is null, the event handler is referred to as direct or directly-bound. The handler is called every time an event occurs on the selected elements, whether it occurs directly on the element or bubbles from a descendant (inner) element.
When a selector is provided, the event handler is referred to as delegated. The handler is not called when the event occurs directly on the bound element, but only for descendants (inner elements) that match the selector. 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.
In this case, you want to delegate the event since your element is not yet available in the DOM when you're binding the event.
Don't use the click(), use on('click') and attach it to the document.
Creating a handler this way, will ensure that any new elements will be able to trigger the event.
$('fight') selects fight tag, not the tag with fight id. Try to use $('#fight') instead.
I want a new text input box will be appended when i click onto the latest generated text box.
But It generates new text input box only when i click the first text input box. So, any solution?
<script type="text/javascript">
$(function(event){
$('.add-new').click(function(){
$('.add-new').removeClass();
$('form').append("<br><input type='text' name='user[]' class='add-new'/>");
});
});
</script>
<div>
<form method='post' name='login'>
<input type='text' name='user[]' class='add-new'/>
</form>
</div>
$('form').on('click','.add-new', function(){
Direct event => Delegate Event
Live DEMO
Full code:
$('form').on('click', '.add-new', function() {
$(this).removeClass('add-new');
$(this).closest('form').append("<br><input type='text' name='user[]' class='add-new'/>");
});
Event handlers are bound only to the currently selected elements; they must exist on the page at the time your code makes the call to .on(). To ensure the elements are present and can be selected, perform event binding inside a document ready handler for elements that are in the HTML markup on the page. If new HTML is being injected into the page, select the elements and attach event handlers after the new HTML is placed into the page. Or, use delegated events to attach an event handler, as described next.
Delegated events have the advantage that they can process events from descendant elements that are added to the document at a later time. By picking an element that is guaranteed to be present at the time the delegated event handler is attached, you can use delegated events to avoid the need to frequently attach and remove event handlers.
on docs
demo http://jsfiddle.net/JuvwB/8/
Plz note: you should use $(this) as your even is bind to .add-new already.
rest all the above are nice solutions,
Hope this helps, cheers
code
$(function(event){
$('.add-new').on('click', function(){
$(this).removeClass();
$('form').append("<br><input type='text' name='user[]' class='add-new'/>");
});
});
$('form[name=login]').on('click', '.add-new', function() {
$(this).removeClass(); // $(this) instead of $('.add-new')
// $(this) point to the clicked element
// which you want
$('form').append("<br><input type='text' name='user[]' class='add-new'/>");
});
As you're changing the class name add-new and append new element dynamically with same class, so you need delegate event.
Read more about .on()
Note
syntax of .on() for delegate event
$(container).on(eventName, target, handlerFunction)
The reason why this doesn't work is because when you set the 'click' event your target doesn't exist, so no 'click' event is bound to it.
jQuery has a fancy function called the 'on' function that catches bubbling events.
$(document).on('click','.add-new', function(){
}
All events (click, mouseover, etc) start in the deepest node and bubble up through the html tree until the document. It is safe for you to catch them in the document, unless you explicitly call "stopPropagation" or return false on a processed in the middle of the bubling click handler function.
You can also catch it in the middle of the tree with $("form").on... or even $("div").on...
When I access <div> or <p> elements by class with jQuery for a click function, it repeats the event by how many elements are in the array or stack. So, if I have 3 <div> elements on top of each other or next to each other, the one on the bottom, or the one to the right, will go through the event once and the one on the top or the left will go through the event 3 times.
Am I doing something wrong? Or is this not meant to be done with jQuery?
[revision]
sorry if i worded this in a confusing way. here is a link... you will better understand my problem there. just add a couple new elements via the form and click on them.
http://jsfiddle.net/rNj6e/
Now that you've posted a fiddle showing the problem, I can actually answer. The problem is that you bind the click event handler to .dp inside the click event handler bound to #add. So what happens is this:
You fill in the form and click #add, which creates a new element with class dp and appends it
It then binds a click event handler to every element with class dp (there's only 1, the 1 we just added)
You fill in the form again, click #add, which repeats steps 1 and 2, so it binds another click event listener to the first .dp element, and binds one to the new element.
Repeat as necessary, binding more and more event handlers to the existing elements every time you click #add!
To fix this, you need to bind the event handler to .dp outside of the #add event handler. The problem is that you're creating new .dp elements on the fly, so just using .click won't bind to elements that are not in the DOM yet. To solve that, you can use delegate, which binds an event handler to elements matching the selector now and in the future:
$("#preview").delegate(".dp", "click", function(event){
alert(this.id);
});
Here's an updated fiddle.
Try:
$(".some_class").click(function(event){
alert(event.target.id);
}).children().click(function(event) {
return false;
});
This should prevent the click event from bubbling through the children, this happens when you click on the children contained in the div.
You are recieving a blank ID because the target of your clicks is most likely the child you clicked and you haven't given it an ID.
To prove this try...
$(".some_class").click(function(event){
alert(event.target.nodeName);
});
which alerts you the nodeName (the name of the html tag) you just clicked.
Change it to this:
$(".some_class").each( function () {
jQuery(this).click(function(event){
alert(event.target.id);
});
});