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Executing an action only once - without disable or one click [duplicate]

I want to check if an element has the class .active, if it does add: margin-top: 4px;
However I only want this to occur once, when the page loads, once the class has been detected I don't want to detect it again and add the CSS style.
This class is applied when certain elements are hovered over.
Is this possible in jQuery?

Check out the one event. Documented example:
$('#foo').one('click', function() {
alert('This will be displayed only once.');
});

This will fire once on page load
$(function(){
if ($("#elementid").hasClass("active"))
{
$("#elementid").css("margin-top", "4px");
}
});

The way I usually do this is:
(function($) {
// my custom function to process elements
function myProcessFunction(context) {
// get context
context = context || document;
// select elements within the context, filter out already processed ones
// loop through remained (unprocessed) elements
// '.my-class' - selector for the elements I want to process
$('.my-class:not(.my-class-processed)', context).each( function(i.e){
// mark the element as processed
$(e).addClass('my-class-processed');
// add process code here
});
}
// run myProcessFunction on document.ready
$(document).ready( function(){
myProcessFunction();
});
})(jQuery);
This way I have:
reusable function
processed elements are marked and won't be processed next time the function is called
elements are processed within the context only, if specified (for instance, HTML code returned via an AJAX request)
Hope this helps )

JQuery select elements in <span> that doesn't exist initially

I've been looking for so long and found several answers that suggest using .on() as in $('.idOfMyElemenet').on() works even for elements that don't exist yet. But this doesn't seem to be finding the element. Am I doing something wrong?
The highest level <span> (in screenshot) does not exist until I click on a drop-down. Ultimately I'm trying to trigger an event when the user clicks on any of the <li> (aka selects an option from the drop-down).
$(document).ready(function () {
var test = "#select2-id_customer-results";
$(test).on("click", function() {
console.log('hello')
})
})
EDIT:
Thanks to Drew Baker - I think his second solution is the way to go. But not quite there yet...
From the select2 documentation
All public events are relayed using the jQuery event system, and they
are triggered on the <select> element that Select2 is attached to.
So I tried listening to it via the id (which doesn't seem to exist but would probably be id_customer) and the class. The class I added below did not work. Is there a way to listen to this using Jquery?
$(document).ready(function () {
// console.log($('#id_customer'));
$('.modelselect2 form-control select2-hidden-accessible').on('select2:select', function (e) {
var data = e.params.data;
console.log(data);
});
});

I'll answer your question, but then give you a better solution.
First, you need to make sure the thing you are attaching .on() to actually exists. I typically use a containing DIV or failing that body or html will work.
Secondly you are missing a parameter that tells jQuery the thing you are looking to watch to be clicked on. In this case, I'm assuming it is the UL tag with the ID you provided.
This should do what you want:
$(document).ready(function () {
$('body').on("click", "#select2-id_customer-results", function() {
console.log('hello')
})
})
But a better solution would be to use the Select2 API to have it tell you when something is selected. This will be way more reliable and should make your code work after upgrades to Select2.
Something like this:
$('select[name="customer"]').on('select2:select', function (e) {
var data = e.params.data;
console.log(data);
});
NOTE: #mySelect2 is probably not what you have. Use whatever ID you used to initialize Select2 in jQuery.
You can read more about that API here: https://select2.org/programmatic-control/events

if your element is dynamically generated and you want to target that specific element. You need to specify a static container/parent element to indicate where it belongs.
Try this:
$( '#dynamicallyAddedElement' ).on( 'click', '#wrapper', function () { ... });
//where #wrapper is a static parent element in which you add the dynamic links.
So, you have a wrapper which is hard-coded into the HTML source code:
PS. Hope I helped in some way.

If you need to trigger an event when click on <li> elements, you have to use that elements id or class as the selector. Check the below code:
$(document).ready(function () {
var test = ".select2-results__option";
$(test).on("click", function() {
console.log('hello')
})
})

It turns out this is an old bug in django-auto-complete.
The code below works. I have no idea why but now I can move on.
Note: the 'name' is the value of the select2 select element (see screenshot at bottom)
document.querySelector('select[name="customer"]').onchange=function() {
console.log("myselect2name changed");
};

how to remove all ClientEvents from anchors in an HTML String with jQuery

I've been struggling with what seems to be a simple problem for a few hours now. I've written a REGEX expression that works however I was hoping for a more elegant approach for dealing with the HTML. The string would be passed in to the function, rather than dealing with the content directly in the page. After looking at many examples I feel like I must be doing something wrong. I'm attempting to take a string and clean it of client Events before saving it to our Database, I thought jQuery would be perfect for this.
I Want:
Some random text click here and a link with any event type
//to become:
Some random text click here and a link with any event type
Here's my code
function RemoveEvilScripts(){
var myDiv = $('<div>').html('testing this Do it! out');
//remove all the different types of events
$(myDiv).find('a').unbind();
return $(myDiv).html();
}
My results are, the onClick remains in the anchor tag.

Here's a pure Javascript solution that removes any attribute from any DOM element (and its children) that starts with "on":
function cleanHandlers(el) {
// only do DOM elements
if (!('tagName' in el)) return;
// attributes is a live node map, so don't increment
// the counter when removing the current node
var a = el.attributes;
for (var i = 0; i < a.length; ) {
if (a[i].name.match(/^on/i)) {
el.removeAttribute(a[i].name);
} else {
++i;
}
}
// recursively test the children
var child = el.firstChild;
while (child) {
cleanHandlers(child);
child = child.nextSibling;
}
}
cleanHandlers(document.body);​
working demo at http://jsfiddle.net/alnitak/dqV5k/

unbind() doesn't work because you are using inline onclick event handler. If you were binding your click event using jquery/javascript the you can unbind the event using unbind(). To remove any inline events you can just use removeAttr('onclick')
$('a').click(function(){ //<-- bound using script
alert('clicked');
$('a').unbind(); //<-- will unbind all events that aren't inline on all anchors once one link is clicked
});
http://jsfiddle.net/LZgjF/1/

I ended up with this solution, which removes all events on any item.
function RemoveEvilScripts(){
var myDiv = $('<div>').html('testing this Do it! out');
//remove all the different types of events
$(myDiv)
.find('*')
.removeAttr('onload')
.removeAttr('onunload')
.removeAttr('onblur')
.removeAttr('onchange')
.removeAttr('onfocus')
.removeAttr('onreset')
.removeAttr('onselect')
.removeAttr('onsubmit')
.removeAttr('onabort')
.removeAttr('onkeydown')
.removeAttr('onkeypress')
.removeAttr('onkeyup')
.removeAttr('onclick')
.removeAttr('ondblclick')
.removeAttr('onmousedown')
.removeAttr('onmousemove')
.removeAttr('onmouseout')
.removeAttr('onmouseover')
.removeAttr('onmouseup');
return $(myDiv).html();
}

jquery or js code to obtain exact node data for currently selected form item/text/image in a web page

I want to obtain the exact details for the item on a web page that has been clicked on, using jquery.
That item can be a form item (like a checkbox, text box, text area etc) or section of text (in a paragraph or div or other) or list or image ...
What I figured out is the following--
$(function(){
$('*')
.bind('click', function(event) {
//now obtain details of item that has been clicked on...
});
});
Now, I want the exact details- viz the div id/form id/paragraph #, ie all details for that particular item. How do i get this data? I understand that this data is available in the DOM but I just dont know how to get it in this particular case...

Probably the best way to do to use the target property of the event. By default, this returns a non-jQuery object, which isn't particularly useful, however wrapping it in $() solves this issue:
$(function() {
$(document).bind('click', function(event) {
var element = $(event.target);
alert(element.height()); // Get height
alert(element.attr('id')); // Get ID attribute
// ...
});
});
If you want to fix your current method, inside your click() handler, you can access the properties of that element using .attr(), and friends:
$(function() {
$('*').bind('click', function(event) {
alert($(this).height()); // Get height
alert($(this).attr('id')); // Get ID attribute
// ...
});
});
$(this) in the scope of the function references the element that was clicked. There is a list of functions that will return attributes here and here in the jQuery docs. $.attr('id') will return the element's ID, among other things, and $.data() will return data-* attributes.
To get attributes of parent elements, simply use $(this).parent(). For example, to get the ID of the form that contains the clicked element, use $(this).closest('form').attr('id');. Everything is relative to the clicked element ($(this)), so you can just use the DOM traversal functions.
However, using $('*').bind() is incredibly inefficient; you're binding an event handler to every element on the page, when really you should delegate events with .on() (jQuery 1.7+):
$(function() {
$('body').on('click', '*', function(event) {
alert($(this).height()); // Get height
alert($(this).attr('id')); // Get ID attribute
// ...
});
});
This approach only binds one event to <body> instead of an event to every element on the page.

Use the target of click event on page
$(document).click(function(event){
/* store native dom node*/
var tgt=event.target;
/* store jQuery object of dom node*/
var $tgt=$(tgt);
/* example element details*/
var details={ id : tgt.id, height: $tgt.height(), tag : tgt.tagName}
console.log( details)
})

Look at the event.target, and then you can use jQuery's .parents() method to look at every ancestor:
$(document).on('click', function(event) {
var $t = $(event.target); // the element that was actually clicked
var $p = $t.parents(); // the target's parents
var $form = $p.filter('form').first(); // the enclosing form, if it exists
});

preventing effects to be applied to the same object twice when adding objects with ajax

I'm having a little issue with an application I'm making. I have a page where the user edits a document via dragging modules into the page or "canvas" area.
http://thinktankdesign.ca/temp_img.jpg
When the page is loaded, javascript haves the modules collapsible (like above). However after the user drags in a new module the effect is applied again some new modules can collapse as well. here is the problem. each time a module loads the same effect gets applied to the modules that already can collapse. It ends up breaking their animations.
heres the code that gets executed on page load.
//make colapsible
$("h1.handle").click(function() {
var object = $(this);
v$(this).next().toggle("fast", colapsible_class(object));
vreturn false;
}).addClass("open");
and heres the code that gets executed in the creation of a module via ajax
function get_module(id){
var template = $('input[name=template]').val();
$.post(window.location.href, { template: template, module: id, mode: 'create' },
function(data){
$(data).insertBefore(".target_wrapper");
//enable deletion of module
$(".js_no_modules").slideUp("slow");
$(enable_module_deletion());
//show delete button
$("button[name=delete]").show();
//make colapsible
$("h1.handle").click(function() {
var object = $(this);
$(this).next().toggle("fast", colapsible_class(object));
return false;
}).addClass("open");
}
);
}
I need a solid way of preventing the toggle effect to be applied to the same module twice

Use jQuery 1.3 live events instead.
//make colapsible
$("h1.handle").live("click", function() {
var object = $(this);
v$(this).next().toggle("fast", colapsible_class(object));
vreturn false;
}).addClass("open");
and then eliminate the click declaration in the second block of code, changing it to $("h1.handle").addClass("open");
Live events bind all current and future matching elements with an event.

In your Ajax success handler try the following:
//make collapsible
$("h1.handle:not(.open)").click(function() {
var object = $(this);
$(this).next().toggle("fast", colapsible_class(object));
return false;
}).addClass("open");

The best way to solve your problem is, instead of using $("h1.handle") on the AJAX callback, go for $(data).find("h1.handle"). Something like,
var x = $(data);
x.insertBefore(...);
/* your other code */
x.find('h1.handle').click(...).addClass(...);
Like that, only the newly added items will have the event bounded. The already present ones will not be touched.
If we want to answer your question instead of just solving your problem, then we have several alternatives, such as:
store, in your objects, that the onclick event handler has been set so that you don't set it twice
always bind the onclick event, but always unbind it first
use jQuery's live events and the addClass open only on the newly created items.
IMO, the first one is the easiest. You can accomplish it by using jQuery's data(). Then you could do something like:
$("h1.handle").each(function() {
var me = $(this);
// if already has click handler, don't do anything
if (me.data('click_set') != null) { return true; }
// otherwise, store the data and bind the click event
me.data('click_set', true).click(function() {
/* the code you already have on the click handler */
}).addClass('open');
}
The second alternative involves storing the function that you pass inline to the click event binder in a variable, and then using jQuery's unbind to disable it.