Setting onclick event removing the handlers attached before - javascript

What is the difference betwen setting the onclick function in this way:
obj.onclick=new Function('functionname')
and
obj.onclick=function(){ functionname();};
How can i set the onclick event removing all previrius attached? (using jquery or simply javascript)
i try something like this:
$(obj).unbind('click');
$(obj).click(function() {
functionname();
});
but the unbind seems to remove even the next attached events.
thanks
EDIT:
I set the click event using jquery:
function ON(){
$('#makecorr').unbind('click');//i unbind for some reason..
$('#makecorr').click(function() { OFF(); });
}
function OFF(){
$('#makecorr').unbind('click');//i want to remove prev attached fun
//and replace it with new event
$('#makecorr').click(function() { ON(); });
}
this doesnt work for me, when i click the object 'makecorr' it goes in loop , if i put an alert, it comes up infinitely
but when i use: '
function ON(){
$('#makecorr').get(0).onclick=new Function('OFF()');
}
function OFF()
{
$('#makecorr').get(0).onclick=new Function('ON()');
}
it works. strange where am i wrong?

This pair of lines:
$(obj).unbind('click');
$(obj).click(function() { functionname(); });
...if executed in the order above should result in just the handler you've defined there being attached. If you're seeing other behavior, it must be something else in the script.
Regarding
What is the difference betwen setting the onclick function in this way:
obj.onclick=new Function('functionname') and
obj.onclick=function(){ functionname();};
If you're dynamically adding handlers to an element and you're already using jQuery for other reasons, you don't want to use the onclick property at all; stick to the jQuery API, to avoid really confusing yourself. :-)
Even if you're not using jQuery, you almost never want to use new Function(...). There are only very special situations where you'd need that. Mostly stick to function() { functionname(); } (or just use functionname directly).

Related

Changed data attribute not recognized in jquery selector

I've the following html structure
<body data-page="first">
<div class="start">Test</div>
</body>
and the following js
$('body[data-page="first"] .start').on('click',function (){
body.attr('data-page','second');
});
$('body[data-page="second"] .start').on('click',function (){
console.log('Test');
});
I would expect, that after the second click on .start, the console would show "Test", but it doesn't...
Can you tell me what I'm doing wrong?
Thanks in advance!
While you have your answer, I don't think the essential point has been made in any of the answers so far, and that is that the binding of an event handler must happen after the target element exists.
When you try to bind an event handler to a particular element in the DOM, the element must exist at the time. If it does not exist, the handler has nothing to bind to, and so the binding fails. If you later create the element, it's too late, unless you re-run the binding statement.
It will soon become second nature to call appropriate event handler binding statements after you create a new element (by modifying the HTML using javascript) that needs a handler.
For instance, in my current project I regularly make AJAX calls to a server to replace blocks of HTML as things happen on the page. Even if some of the new elements are exactly the same as the ones being replaced, they will not inherit any bindings from the replaced elements. Whenever I update the HTML I call a function that contains necessary statements to bind my event handlers to the new copy of the active elements.
Your code would work if you made the following change:
$('body[data-page="first"] .start').on('click',function ()
{
body.attr('data-page','second');
$('body[data-page="second"] .start').on('click',function (){
console.log('Test');
});
})
A couple of other (off-topic, but related) points:
It's possible to bind a handler to an element multiple times. The trick to avoiding this is to include the .off() method in the chain before binding (noting though that .off("click") will unbind all click handlers bound to that element, not just yours) e.g.
$("#mybutton").off("click").click(function(){myHandler()});
"the arrow function doesn’t have its own 'this' value" () so don't use arrow functions in event handlers if you plan to reference any of the element's properties via 'this'. e.g.
$("#mybutton").off("click").click(() => {console.log(${this.id})}); // >> "undefined"
The issue is that the page is rendered with the data-page set to first, and when you click again on it, that part of javascript still see "first", since is not rerendered, so you need a dynamic function, the read all the intereaction with that button, and than check wich value that attribute has. Like this you can make infinite cases, and still go on.
$('body .start').on('click',function (){
const attr = $('body').attr('data-page');
if(attr === 'first') {
$('body').attr('data-page','second');
} else {
console.log('second');
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<body data-page="first">
<div class="start">Test</div>
</body>
And if you don't like the fact that is targetting all the "body" wich is weird, becouse you should have only 1 body, you can use an ID to target the right one
PS: is never a good idea to duplicate your function, if you can set everything in a dynamic function, that reads everything, is easier to debug in the feature, and is lighter and more clean to work on
$('body[data-page="first"] .start').click(function (){
var body = $('body[data-page="first"] .start');
body.attr('data-page','second');
});
This method can help :
var timesClicked = 0;
$('.start').on('click',function (){
timesClicked++;
if (timesClicked>1) {
console.log('Test');
}
});

jQuery remove scroll listener after reach certain point [duplicate]

I have an input type="image". This acts like the cell notes in Microsoft Excel. If someone enters a number into the text box that this input-image is paired with, I setup an event handler for the input-image. Then when the user clicks the image, they get a little popup to add some notes to the data.
My problem is that when a user enters a zero into the text box, I need to disable the input-image's event handler. I have tried the following, but to no avail.
$('#myimage').click(function { return false; });
jQuery ≥ 1.7
With jQuery 1.7 onward the event API has been updated, .bind()/.unbind() are still available for backwards compatibility, but the preferred method is using the on()/off() functions. The below would now be,
$('#myimage').click(function() { return false; }); // Adds another click event
$('#myimage').off('click');
$('#myimage').on('click.mynamespace', function() { /* Do stuff */ });
$('#myimage').off('click.mynamespace');
jQuery < 1.7
In your example code you are simply adding another click event to the image, not overriding the previous one:
$('#myimage').click(function() { return false; }); // Adds another click event
Both click events will then get fired.
As people have said you can use unbind to remove all click events:
$('#myimage').unbind('click');
If you want to add a single event and then remove it (without removing any others that might have been added) then you can use event namespacing:
$('#myimage').bind('click.mynamespace', function() { /* Do stuff */ });
and to remove just your event:
$('#myimage').unbind('click.mynamespace');
This wasn't available when this question was answered, but you can also use the live() method to enable/disable events.
$('#myimage:not(.disabled)').live('click', myclickevent);
$('#mydisablebutton').click( function () { $('#myimage').addClass('disabled'); });
What will happen with this code is that when you click #mydisablebutton, it will add the class disabled to the #myimage element. This will make it so that the selector no longer matches the element and the event will not be fired until the 'disabled' class is removed making the .live() selector valid again.
This has other benefits by adding styling based on that class as well.
This can be done by using the unbind function.
$('#myimage').unbind('click');
You can add multiple event handlers to the same object and event in jquery. This means adding a new one doesn't replace the old ones.
There are several strategies for changing event handlers, such as event namespaces. There are some pages about this in the online docs.
Look at this question (that's how I learned of unbind). There is some useful description of these strategies in the answers.
How to read bound hover callback functions in jquery
If you want to respond to an event just one time, the following syntax should be really helpful:
$('.myLink').bind('click', function() {
//do some things
$(this).unbind('click', arguments.callee); //unbind *just this handler*
});
Using arguments.callee, we can ensure that the one specific anonymous-function handler is removed, and thus, have a single time handler for a given event. Hope this helps others.
maybe the unbind method will work for you
$("#myimage").unbind("click");
I had to set the event to null using the prop and the attr. I couldn't do it with one or the other. I also could not get .unbind to work. I am working on a TD element.
.prop("onclick", null).attr("onclick", null)
If event is attached this way, and the target is to be unattached:
$('#container').on('click','span',function(eo){
alert(1);
$(this).off(); //seams easy, but does not work
$('#container').off('click','span'); //clears click event for every span
$(this).on("click",function(){return false;}); //this works.
});​
You may be adding the onclick handler as inline markup:
<input id="addreport" type="button" value="Add New Report" onclick="openAdd()" />
If so, the jquery .off() or .unbind() won't work. You need to add the original event handler in jquery as well:
$("#addreport").on("click", "", function (e) {
openAdd();
});
Then the jquery has a reference to the event handler and can remove it:
$("#addreport").off("click")
VoidKing mentions this a little more obliquely in a comment above.
If you use $(document).on() to add a listener to a dynamically created element then you may have to use the following to remove it:
// add the listener
$(document).on('click','.element',function(){
// stuff
});
// remove the listener
$(document).off("click", ".element");
To remove ALL event-handlers, this is what worked for me:
To remove all event handlers mean to have the plain HTML structure without all the event handlers attached to the element and its child nodes. To do this, jQuery's clone() helped.
var original, clone;
// element with id my-div and its child nodes have some event-handlers
original = $('#my-div');
clone = original.clone();
//
original.replaceWith(clone);
With this, we'll have the clone in place of the original with no event-handlers on it.
Good Luck...
Updated for 2014
Using the latest version of jQuery, you're now able to unbind all events on a namespace by simply doing $( "#foo" ).off( ".myNamespace" );
Best way to remove inline onclick event is $(element).prop('onclick', null);
Thanks for the information. very helpful i used it for locking page interaction while in edit mode by another user. I used it in conjunction with ajaxComplete. Not necesarily the same behavior but somewhat similar.
function userPageLock(){
$("body").bind("ajaxComplete.lockpage", function(){
$("body").unbind("ajaxComplete.lockpage");
executePageLock();
});
};
function executePageLock(){
//do something
}
In case .on() method was previously used with particular selector, like in the following example:
$('body').on('click', '.dynamicTarget', function () {
// Code goes here
});
Both unbind() and .off() methods are not going to work.
However, .undelegate() method could be used to completely remove handler from the event for all elements which match the current selector:
$("body").undelegate(".dynamicTarget", "click")
I know this comes in late, but why not use plain JS to remove the event?
var myElement = document.getElementById("your_ID");
myElement.onclick = null;
or, if you use a named function as an event handler:
function eh(event){...}
var myElement = document.getElementById("your_ID");
myElement.addEventListener("click",eh); // add event handler
myElement.removeEventListener("click",eh); //remove it
This also works fine .Simple and easy.see http://jsfiddle.net/uZc8w/570/
$('#myimage').removeAttr("click");
if you set the onclick via html you need to removeAttr ($(this).removeAttr('onclick'))
if you set it via jquery (as the after the first click in my examples above) then you need to unbind($(this).unbind('click'))
All the approaches described did not work for me because I was adding the click event with on() to the document where the element was created at run-time:
$(document).on("click", ".button", function() {
doSomething();
});
My workaround:
As I could not unbind the ".button" class I just assigned another class to the button that had the same CSS styles. By doing so the live/on-event-handler ignored the click finally:
// prevent another click on the button by assigning another class
$(".button").attr("class","buttonOff");
Hope that helps.
Hope my below code explains all.
HTML:
(function($){
$("#btn_add").on("click",function(){
$("#btn_click").on("click",added_handler);
alert("Added new handler to button 1");
});
$("#btn_remove").on("click",function(){
$("#btn_click").off("click",added_handler);
alert("Removed new handler to button 1");
});
function fixed_handler(){
alert("Fixed handler");
}
function added_handler(){
alert("new handler");
}
$("#btn_click").on("click",fixed_handler);
$("#btn_fixed").on("click",fixed_handler);
})(jQuery);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button id="btn_click">Button 1</button>
<button id="btn_add">Add Handler</button>
<button id="btn_remove">Remove Handler</button>
<button id="btn_fixed">Fixed Handler</button>
I had an interesting case relevant to this come up at work today where there was a scroll event handler for $(window).
// TO ELIMINATE THE RE-SELECTION AND
// RE-CREATION OF THE SAME OBJECT REDUNDANTLY IN THE FOLLOWING SNIPPETS
let $window = $(window);
$window.on('scroll', function() { .... });
But, to revoke that event handler, we can't just use
$window.off('scroll');
because there are likely other scroll event handlers on this very common target, and I'm not interested in hosing that other functionality (known or unknown) by turning off all of the scroll handlers.
My solution was to first abstract the handler functionality into a named function, and use that in the event listener setup.
function handleScrollingForXYZ() { ...... }
$window.on('scroll', handleScrollingForXYZ);
And then, conditionally, when we need to revoke that, I did this:
$window.off('scroll', $window, handleScrollingForXYZ);
The janky part is the 2nd parameter, which is redundantly selecting the original selector. But, the jquery documentation for .off() only provides one method signature for specifying the handler to remove, which requires this middle parameter to be
A selector which should match the one originally passed to .on() when attaching event handlers.
I haven't ventured to test it out with a null or '' as the 2nd parameter, but perhaps the redundant $window isn't necessary.

Event handler does not fire with .on(), but works with .delegate()

I'm using a Bootstrap Modal dialog, and I have an event handler set up so that once the modal closes, it triggers a couple of other updates on the page. I had been using the .delegate method which works perfectly. After reading that it was deprecated, I tried to move to the .on method, however the handler was not getting triggered. I cannot figure out why. Here are my two code snippets for comparison:
Delegate:
$(document).delegate('#streamingPopup', 'hide.bs.modal', function () { ... });
On:
$('#streamingPopup').on('hide.bs.modal', function () { ... });
No code withing the callback function has changed.
As far as I can tell, I'm using it the way the documentation says it should be used (http://api.jquery.com/on/). I'm assuming it has something to do with the hide.bs.modal event, or with the fact that it's attached directly to the jQuery object rather than the DOM itself, but I can't work out why it would work in one but not the other. Can anyone point me to what I'm doing wrong?
You might need to change the syntax for .on:
$(document).on('hide.bs.modal', '#streamingPopup', function () { ... });
This must work, as it targets a static parent. Replace the document with a static parent of #streamingPopup.

when you create an object which has events, but isnt added to the page, it doesnt save handlers

I have a fiddle which creates a viewer for a set of data. If you are looking at the javascript, it will look at 3 lines, if you search for SEARCH_HERE
$("body").append("TEMPLATE<hr />Maintaining Object").append($maintence);
//$("body").html($maintence);
//$("body").html($_table);
The fiddle is located at: http://jsfiddle.net/fallenreaper/wFGW6/1/
The first one will show the TEMPLATE on the page and then adding new ITEMS will all have working events when doing
var $data = $_table.clone(true,true);
in the addBlock() function.
If you only uncomment the second line, it will JUST show the maintainer item.
When you add items [+], you will show the form, but the events would not be there.
I was thinking that since $_table is removed from the page, the events are not there any longer. The 3rd line, pretty much reappends $_table to the document, and the events are not there.
IS this suppose to be like this? Should i instead just create a wrapper function which is executed inside of addBlock() to attach all the handlers accordingly?
This is rather odd.
EDIT:
One answer, pointed to delegated events, which seems like it could work. There is an issue though that seems to set $(this) to a new object, the body tag, instead of the selected element.
inside of a click event would be redefined as:
$("body").on("click", $expander, function(){...});
//instead of:
//$expander.click(function(){...});
I was thinking to just do something like left-hand assignment, something like:
$(this) = $expander;
but according to a website, left-hand assignment doesnt work. (http://hungred.com/how-to/tutorial-override-this-object-javascript/). They did point me in a direction which would be VERY useful.
function example(eventHandler){
ALL MY CODE.
}
$("body").on("click", $expander, function(event){
example.call($expander, event);
});
Does this look feasible, or should i be planning another route?
You can use jQuery's .on() to do some event delegation. Your code is too long for me to read and edit, but in a nutshell rather than having $add.click(function() { ... }) you bind the event listener to the parent or body $("body").on("click", ".addNew", function() { ... })

Intercept javascript event

Here's what I'm trying to do :
I have a page with some links. Most links have a function attached to them on the onclick event.
Now, I want to set a css class to some links and then whenever one of the links is clicked I want to execute a certain function - after it returns , I want the link to execute the onclick functions that were attached to it.
Is there a way to do what I want ? I'm using jQuery if it makes a difference.
Here's an attempt at an example :
$("#link").click(function1);
$("#link").click(function2);
$("#link").click(function(){
firstFunctionToBeCalled(function (){
// ok, now execute function1 and function2
});
}); // somehow this needs to be the first one that is called
function firstFunctionToBeCalled(callback){
// here some user input is expected so function1 and function2 must not get called
callback();
}
All this is because I'm asked to put some confirmation boxes (using boxy) for a lot of buttons and I really don't want to be going through every button.
If I understand you correctly, is this wat you wanted to do..
var originalEvent = page.onclick; //your actual onclick method
page.onclick = handleinLocal; //overrides this with your locaMethod
function handleinLocal()
{ ...your code...
originalEvent ();
// invoke original handler
}
I would use jQuery's unbind to remove any existing events, then bind a function that will orchestrate the events I want in the order I want them.
Both bind and unbind are in the jQuery docs on jquery.com and work like this...
$(".myClass").unbind("click"); // removes all clicks - you can also pass a specific function to unbind
$(".myClass").click(function() {
myFunctionA();
myFunctionB($(this).html()); // example of obtaining something related to the referrer
});
An ugly hack will be to use the mousedown or mouseup events. These will be called before the click event.
If you can add your event handler before the rest of handlers, you could try to use jQuery's stopImmediatePropagation

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