Related
I have an object that has methods in it. These methods are put into the object inside an anonymous function. It looks like this:
var t = {};
window.document.addEventListener("keydown", function(e) {
t.scroll = function(x, y) {
window.scrollBy(x, y);
};
t.scrollTo = function(x, y) {
window.scrollTo(x, y);
};
});
(there is a lot more code, but this is enough to show the problem)
Now I want to stop the event listener in some cases. Therefore I am trying to do a removeEventListener but I can't figure out how to do this. I have read in other questions that it is not possible to call removeEventListener on anonymous functions, but is this also the case in this situation?
I have a method in t created inside the anonymous function and therefore I thought it was possible. Looks like this:
t.disable = function() {
window.document.removeEventListener("keydown", this, false);
}
Why can't I do this?
Is there any other (good) way to do this?
Bonus info; this only has to work in Safari, hence the missing IE support.
You can name the function passed and use the name in the removeEventListener. as in:
button.addEventListener('click', function eventHandler() {
///this will execute only once
alert('only once!');
this.removeEventListener('click', eventHandler);
});
EDIT:
This will not work if you are working in strict mode ("use strict";)
EDIT 2:
arguments.callee is now deprecated (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments/callee)
I believe that is the point of an anonymous function, it lacks a name or a way to reference it.
If I were you I would just create a named function, or put it in a variable so you have a reference to it.
var t = {};
var handler = function(e) {
t.scroll = function(x, y) {
window.scrollBy(x, y);
};
t.scrollTo = function(x, y) {
window.scrollTo(x, y);
};
};
window.document.addEventListener("keydown", handler);
You can then remove it by
window.document.removeEventListener("keydown", handler);
A version of Otto Nascarella's solution that works in strict mode is:
button.addEventListener('click', function handler() {
///this will execute only once
alert('only once!');
this.removeEventListener('click', handler);
});
in modern browsers you can do the following...
button.addEventListener( 'click', () => {
alert( 'only once!' );
}, { once: true } );
https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#Parameters
window.document.removeEventListener("keydown", getEventListeners(window.document.keydown[0].listener));
May be several anonymous functions, keydown1
Warning: only works in Chrome Dev Tools & cannot be used in code: link
There's a new way to do this that is supported by the latest versions of most popular browsers with the exception of Safari.
Check caniuse for updated support.
Update: Now also supported by Sefari (version 15^).
We can add an option to addEventListner called signal and assign a signal from an AbortController on which you can later call the abort() method.
Here is an example.
We create an AbortController:
const controller = new AbortController();
Then we create the eventListner and pass in the option signal:
document.addEventListener('scroll',()=>{
// do something
},{signal: controller.signal})
And then to remove the eventListner at a later time, we call:
controller.abort()
This is not ideal as it removes all, but might work for your needs:
z = document.querySelector('video');
z.parentNode.replaceChild(z.cloneNode(1), z);
Cloning a node copies all of its attributes and their values, including
intrinsic (in–line) listeners. It does not copy event listeners added using
addEventListener()
Node.cloneNode()
A not so anonymous option
element.funky = function() {
console.log("Click!");
};
element.funky.type = "click";
element.funky.capt = false;
element.addEventListener(element.funky.type, element.funky, element.funky.capt);
// blah blah blah
element.removeEventListener(element.funky.type, element.funky, element.funky.capt);
Since receiving feedback from Andy (quite right, but as with many examples, I wished to show a contextual expansion of the idea), here's a less complicated exposition:
<script id="konami" type="text/javascript" async>
var konami = {
ptrn: "38,38,40,40,37,39,37,39,66,65",
kl: [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ]
};
document.body.addEventListener( "keyup", function knm ( evt ) {
konami.kl = konami.kl.slice( -9 );
konami.kl.push( evt.keyCode );
if ( konami.ptrn === konami.kl.join() ) {
evt.target.removeEventListener( "keyup", knm, false );
/* Although at this point we wish to remove a listener
we could easily have had multiple "keyup" listeners
each triggering different functions, so we MUST
say which function we no longer wish to trigger
rather than which listener we wish to remove.
Normal scoping will apply to where we can mention this function
and thus, where we can remove the listener set to trigger it. */
document.body.classList.add( "konami" );
}
}, false );
document.body.removeChild( document.getElementById( "konami" ) );
</script>
This allows an effectively anonymous function structure, avoids the use of the practically deprecated callee, and allows easy removal.
Incidentally: The removal of the script element immediately after setting the listener is a cute trick for hiding code one would prefer wasn't starkly obvious to prying eyes (would spoil the surprise ;-)
So the method (more simply) is:
element.addEventListener( action, function name () {
doSomething();
element.removeEventListener( action, name, capture );
}, capture );
To give a more up-to-date approach to this:
//one-time fire
element.addEventListener('mousedown', {
handleEvent: function (evt) {
element.removeEventListener(evt.type, this, false);
}
}, false);
JavaScript: addEventListener
method registers the specified listener on the EventTarget(Element|document|Window) it's called on.
EventTarget.addEventListener(event_type, handler_function, Bubbling|Capturing);
Mouse, Keyboard events Example test in WebConsole:
var keyboard = function(e) {
console.log('Key_Down Code : ' + e.keyCode);
};
var mouseSimple = function(e) {
var element = e.srcElement || e.target;
var tagName = element.tagName || element.relatedTarget;
console.log('Mouse Over TagName : ' + tagName);
};
var mouseComplex = function(e) {
console.log('Mouse Click Code : ' + e.button);
}
window.document.addEventListener('keydown', keyboard, false);
window.document.addEventListener('mouseover', mouseSimple, false);
window.document.addEventListener('click', mouseComplex, false);
removeEventListener
method removes the event listener previously registered with EventTarget.addEventListener().
window.document.removeEventListener('keydown', keyboard, false);
window.document.removeEventListener('mouseover', mouseSimple, false);
window.document.removeEventListener('click', mouseComplex, false);
caniuse
I have stumbled across the same problem and this was the best solution I could get:
/*Adding the event listener (the 'mousemove' event, in this specific case)*/
element.onmousemove = function(event) {
/*do your stuff*/
};
/*Removing the event listener*/
element.onmousemove = null;
Please keep in mind I have only tested this for the window element and for the 'mousemove' event, so there could be some problems with this approach.
Possibly not the best solution in terms of what you are asking. I have still not determined an efficient method for removing anonymous function declared inline with the event listener invocation.
I personally use a variable to store the <target> and declare the function outside of the event listener invocation eg:
const target = document.querySelector('<identifier>');
function myFunc(event) {
function code;
}
target.addEventListener('click', myFunc);
Then to remove the listener:
target.removeEventListener('click', myFunc);
Not the top recommendation you will receive but to remove anonymous functions the only solution I have found useful is to remove then replace the HTML element. I am sure there must be a better vanilla JS method but I haven't seen it yet.
I know this is a fairly old thread, but thought I might put in my two cents for those who find it useful.
The script (apologies about the uncreative method names):
window.Listener = {
_Active: [],
remove: function(attached, on, callback, capture){
for(var i = 0; i < this._Active.length; i++){
var current = this._Active[i];
if(current[0] === attached && current[1] === on && current[2] === callback){
attached.removeEventListener(on, callback, (capture || false));
return this._Active.splice(i, 1);
}
}
}, removeAtIndex(i){
if(this._Active[i]){
var remove = this._Active[i];
var attached = remove[0], on = remove[1], callback = remove[2];
attached.removeEventListener(on, callback, false);
return this._Active.splice(i, 1);
}
}, purge: function(){
for(var i = 0; i < this._Active.length; i++){
var current = this._Active[i];
current[0].removeEventListener(current[1], current[2]);
this._Active.splice(i, 1);
}
}, declare: function(attached, on, callback, capture){
attached.addEventListener(on, callback, (capture || false));
if(this._Active.push([attached, on, callback])){
return this._Active.length - 1;
}
}
};
And you can use it like so:
// declare a new onclick listener attached to the document
var clickListener = Listener.declare(document, "click" function(e){
// on click, remove the listener and log the clicked element
console.log(e.target);
Listener.removeAtIndex(clickListener);
});
// completely remove all active listeners
// (at least, ones declared via the Listener object)
Listener.purge();
// works exactly like removeEventListener
Listener.remove(element, on, callback);
I just experienced similiar problem with copy-protection wordpress plugin. The code was:
function disableSelection(target){
if (typeof target.onselectstart!="undefined") //For IE
target.onselectstart=function(){return false}
else if (typeof target.style.MozUserSelect!="undefined") //For Firefox
target.style.MozUserSelect="none"
else //All other route (For Opera)
target.onmousedown=function(){return false}
target.style.cursor = "default"
}
And then it was initiated by loosely put
<script type="text/javascript">disableSelection(document.body)</script>.
I came around this simply by attaching other annonymous function to this event:
document.body.onselectstart = function() { return true; };
Set anonymous listener:
document.getElementById('ID').addEventListener('click', () => { alert('Hi'); });
Remove anonymous listener:
document.getElementById('ID').removeEventListener('click',getEventListeners(document.getElementById('ID')).click[0].listener)
Using the AbortController, neat and clean
Attaching EventListener
const el = document.getElementById('ID')
const controller = new AbortController;
el.addEventListener('click',() => {
console.log("Clicked")
},{signal: controller.signal})
when you want to remove the event listener
controller.abort()
Another alternative workaround to achieve this is adding an empty event handler and preventing event propagation.
Let's assume you need to remove mouseleave event handler from an element which has #specific-div id, that is added with an anonymous function, and you can't use removeEventListener() since you don't have a function name.
You can add another event handler to that element and use event.stopImmediatePropagation(), for being sure this event handler works before existing ones you should pass the third parameter (useCapture) as true.
The final code should look like the below:
document.getElementById("specific-div")
.addEventListener("mouseleave", function(event) {
event.stopImmediatePropagation()
}, true);
This could help for some specific cases that you can't prefer cloneNode() method.
window.document.onkeydown = function(){};
Just question: Is there any way to completely remove all events of an object, e.g. a div?
EDIT: I'm adding per div.addEventListener('click',eventReturner(),false); an event.
function eventReturner() {
return function() {
dosomething();
};
}
EDIT2: I found a way, which is working, but not possible to use for my case:
var returnedFunction;
function addit() {
var div = document.getElementById('div');
returnedFunction = eventReturner();
div.addEventListener('click',returnedFunction,false); //You HAVE to take here a var and not the direct call to eventReturner(), because the function address must be the same, and it would change, if the function was called again.
}
function removeit() {
var div = document.getElementById('div');
div.removeEventListener('click',returnedFunction,false);
}
I am not sure what you mean with remove all events. Remove all handlers for a specific type of event or all event handlers for one type?
Remove all event handlers
If you want to remove all event handlers (of any type), you could clone the element and replace it with its clone:
var clone = element.cloneNode(true);
Note: This will preserve attributes and children, but it will not preserve any changes to DOM properties.
Remove "anonymous" event handlers of specific type
The other way is to use removeEventListener() but I guess you already tried this and it didn't work. Here is the catch:
Calling addEventListener to an anonymous function creates a new listener each time. Calling removeEventListener to an anonymous function has no effect. An anonymous function creates a unique object each time it is called, it is not a reference to an existing object though it may call one. When adding an event listener in this manner be sure it is added only once, it is permanent (cannot be removed) until the object it was added to, is destroyed.
You are essentially passing an anonymous function to addEventListener as eventReturner returns a function.
You have two possibilities to solve this:
Don't use a function that returns a function. Use the function directly:
function handler() {
dosomething();
}
div.addEventListener('click',handler,false);
Create a wrapper for addEventListener that stores a reference to the returned function and create some weird removeAllEvents function:
var _eventHandlers = {}; // somewhere global
const addListener = (node, event, handler, capture = false) => {
if (!(event in _eventHandlers)) {
_eventHandlers[event] = []
}
// here we track the events and their nodes (note that we cannot
// use node as Object keys, as they'd get coerced into a string
_eventHandlers[event].push({ node: node, handler: handler, capture: capture })
node.addEventListener(event, handler, capture)
}
const removeAllListeners = (targetNode, event) => {
// remove listeners from the matching nodes
_eventHandlers[event]
.filter(({ node }) => node === targetNode)
.forEach(({ node, handler, capture }) => node.removeEventListener(event, handler, capture))
// update _eventHandlers global
_eventHandlers[event] = _eventHandlers[event].filter(
({ node }) => node !== targetNode,
)
}
And then you could use it with:
addListener(div, 'click', eventReturner(), false)
// and later
removeAllListeners(div, 'click')
DEMO
Note: If your code runs for a long time and you are creating and removing a lot of elements, you would have to make sure to remove the elements contained in _eventHandlers when you destroy them.
This will remove all listeners from children but will be slow for large pages. Brutally simple to write.
element.outerHTML = element.outerHTML;
Use the event listener's own function remove(). For example:
getEventListeners().click.forEach((e)=>{e.remove()})
As corwin.amber says, there are differences between Webkit an others.
In Chrome:
getEventListeners(document);
Which gives you an Object with all the existing event listeners:
Object
click: Array[1]
closePopups: Array[1]
keyup: Array[1]
mouseout: Array[1]
mouseover: Array[1]
...
From here you can reach the listener you want to remove:
getEventListeners(document).copy[0].remove();
So All the event listeners:
for(var eventType in getEventListeners(document)) {
getEventListeners(document)[eventType].forEach(
function(o) { o.remove(); }
)
}
In Firefox
Is a little bit different because it uses a listener wrapper that contains no remove function. You have to get the listener you want to remove:
document.removeEventListener("copy", getEventListeners(document).copy[0].listener)
All the event listeners:
for(var eventType in getEventListeners(document)) {
getEventListeners(document)[eventType].forEach(
function(o) { document.removeEventListener(eventType, o.listener) }
)
}
I stumbled with this post trying to disable the annoying copy protection of a news website.
Enjoy!
You can add a hook function to intercept all calls to addEventHandler. The hook will push the handler to a list that can be used for cleanup. For example,
if (EventTarget.prototype.original_addEventListener == null) {
EventTarget.prototype.original_addEventListener = EventTarget.prototype.addEventListener;
function addEventListener_hook(typ, fn, opt) {
console.log('--- add event listener',this.nodeName,typ);
this.all_handlers = this.all_handlers || [];
this.all_handlers.push({typ,fn,opt});
this.original_addEventListener(typ, fn, opt);
}
EventTarget.prototype.addEventListener = addEventListener_hook;
}
You should insert this code near the top of your main web page (e.g. index.html). During cleanup, you can loop thru all_handlers, and call removeEventHandler for each. Don't worry about calling removeEventHandler multiple times with the same function. It is harmless.
For example,
function cleanup(elem) {
for (let t in elem) if (t.startsWith('on') && elem[t] != null) {
elem[t] = null;
console.log('cleanup removed listener from '+elem.nodeName,t);
}
for (let t of elem.all_handlers || []) {
elem.removeEventListener(t.typ, t.fn, t.opt);
console.log('cleanup removed listener from '+elem.nodeName,t.typ);
}
}
Note: for IE use Element instead of EventTarget, and change => to function, and various other things.
Clone the element and replace the element with its clone. Events are not cloned.
elem.replaceWith(elem.cloneNode(true));
This uses Node.cloneNode() to clone the elem DOM object, which ignores all event handlers (though, as Jan Turoň's answer notes, attributes like onclick="…" will remain). It then uses Element.replaceWith() to replace elem with that clone. Simple assignment to an anonymous clone wasn't working for me.
This should be faster and cleaner than redefining elem.outerHTML with itself (as proposed by pabombs's answer) but may be slower than answers that iterate through and purge each listener (noting that getEventListeners() seems available exclusively in Chrome's dev console—not elsewhere in Chrome, not at all on Firefox). Presumably, at some higher volume of listeners to clear, this non-loop solution becomes faster.
(This is a simplification of Felix Kling's answer with help from asheroto's comment to it.)
you can add function and remove all other click by assign them
btn1 = document.querySelector(".btn-1")
btn1.addEventListener("click" , _=>{console.log("hello")})
btn1.addEventListener("click" , _=>{console.log("How Are you ?")})
btn2 = document.querySelector(".btn-2")
btn2.onclick = _=>{console.log("Hello")}
btn2.onclick = _=>{console.log("Bye")}
<button class="btn-1">Hello to Me</button>
<button class="btn-2">Hello to Bye</button>
You can indeed remove all event handlers by cloning the node as #FelixKling suggests in his answer, however don't forget that
attribute event handlers are not affected by cloning
Having element like this
<div id="test" onclick="alert(42)">test</div>
will still alert on click after cloning. To remove this sort of events, you need to use removeAttribute method, in general
const removeAttEvents = el =>
[...el.attributes].forEach(att =>
att.name.startsWith("on") && el.removeAttribute(att.name)
);
Then having the test element above, calling removeAttEvents(test) gets rid of the click handler.
To complete the answers, here are real-world examples of removing events when you are visiting websites and don't have control over the HTML and JavaScript code generated.
Some annoying websites are preventing you to copy-paste usernames on login forms, which could easily be bypassed if the onpaste event was added with the onpaste="return false" HTML attribute.
In this case we just need to right click on the input field, select "Inspect element" in a browser like Firefox and remove the HTML attribute.
However, if the event was added through JavaScript like this:
document.getElementById("lyca_login_mobile_no").onpaste = function(){return false};
We will have to remove the event through JavaScript also:
document.getElementById("lyca_login_mobile_no").onpaste = null;
In my example, I used the ID "lyca_login_mobile_no" since it was the text input ID used by the website I was visiting.
Another way to remove the event (which will also remove all the events) is to remove the node and create a new one, like we have to do if addEventListener was used to add events using an anonymous function that we cannot remove with removeEventListener.
This can also be done through the browser console by inspecting an element, copying the HTML code, removing the HTML code and then pasting the HTML code at the same place.
It can also be done faster and automated through JavaScript:
var oldNode = document.getElementById("lyca_login_mobile_no");
var newNode = oldNode.cloneNode(true);
oldNode.parentNode.insertBefore(newNode, oldNode);
oldNode.parentNode.removeChild(oldNode);
Update: if the web app is made using a JavaScript framework like Angular, it looks the previous solutions are not working or breaking the app.
Another workaround to allow pasting would be to set the value through JavaScript:
document.getElementById("lyca_login_mobile_no").value = "username";
At the moment, I don't know if there is a way to remove all form validation and restriction events without breaking an app written entirely in JavaScript like Angular.
Update 2: There is also a way to remove a specific event that was added with addEventListener on a website we don't own, by using the getEventListeners function combined to removeEventListener like mentioned in the answer of Jmakuc. If getEventListeners does not exist like on Firefox, you can use a polyfill and inject the script on the page with Greasemonkey addon: https://github.com/colxi/getEventListeners/issues/1
The only easy way I found and worked is this:
Let's say we want to add 2 event listeners
const element = document.getElementById("element");
element.addEventListener('mouseover',
()=>{
// some task
});
element.addEventListener('mouseout',
()=>{
// some task
});
Now you can remove both of the elements by simply:
element.replaceWith(element.cloneNode(true));
Removing all the events on document:
One liner:
for (key in getEventListeners(document)) { getEventListeners(document)[key].forEach(function(c) { c.remove() }) }
Pretty version:
for (key in getEventListeners(document)) {
getEventListeners(document)[key].forEach(function(c) {
c.remove()
})
}
angular has a polyfill for this issue, you can check. I did not understand much but maybe it can help.
const REMOVE_ALL_LISTENERS_EVENT_LISTENER = 'removeAllListeners';
proto[REMOVE_ALL_LISTENERS_EVENT_LISTENER] = function () {
const target = this || _global;
const eventName = arguments[0];
if (!eventName) {
const keys = Object.keys(target);
for (let i = 0; i < keys.length; i++) {
const prop = keys[i];
const match = EVENT_NAME_SYMBOL_REGX.exec(prop);
let evtName = match && match[1];
// in nodejs EventEmitter, removeListener event is
// used for monitoring the removeListener call,
// so just keep removeListener eventListener until
// all other eventListeners are removed
if (evtName && evtName !== 'removeListener') {
this[REMOVE_ALL_LISTENERS_EVENT_LISTENER].call(this, evtName);
}
}
// remove removeListener listener finally
this[REMOVE_ALL_LISTENERS_EVENT_LISTENER].call(this, 'removeListener');
}
else {
const symbolEventNames = zoneSymbolEventNames$1[eventName];
if (symbolEventNames) {
const symbolEventName = symbolEventNames[FALSE_STR];
const symbolCaptureEventName = symbolEventNames[TRUE_STR];
const tasks = target[symbolEventName];
const captureTasks = target[symbolCaptureEventName];
if (tasks) {
const removeTasks = tasks.slice();
for (let i = 0; i < removeTasks.length; i++) {
const task = removeTasks[i];
let delegate = task.originalDelegate ? task.originalDelegate : task.callback;
this[REMOVE_EVENT_LISTENER].call(this, eventName, delegate, task.options);
}
}
if (captureTasks) {
const removeTasks = captureTasks.slice();
for (let i = 0; i < removeTasks.length; i++) {
const task = removeTasks[i];
let delegate = task.originalDelegate ? task.originalDelegate : task.callback;
this[REMOVE_EVENT_LISTENER].call(this, eventName, delegate, task.options);
}
}
}
}
if (returnTarget) {
return this;
}
};
....
You can add a helper function that clears event listener for example
function clearEventListener(element) {
const clonedElement = element.cloneNode(true);
element.replaceWith(clonedElement);
return clonedElement;
}
just pass in the element to the function and that's it...
Sub-class of EventTarget from the JavaScript WebAPI. Supports removing events without specifying a handler function reference.
class SmartEventTarget extends EventTarget {
constructor() {
super();
this.handlers = {};
}
addEventListener(name, handler) {
super.addEventListener(name, handler);
if (!this.handlers[name]) {
this.handlers[name] = new Set();
}
this.handlers[name].add(handler);
}
removeEventListener(name, handler) {
if (handler) {
super.removeEventListener(name, handler);
this.handlers[name].delete(handler);
} else {
this.handlers[name].forEach(h => {
super.removeEventListener(name, h)
});
this.handlers[name].clear();
}
}
removeAllListeners(name) {
if (name) {
this.removeEventListener(name, null);
} else {
Object.keys(this.handlers).map(name => {
this.removeEventListener(name, null);
});
this.handlers = {};
}
}
}
See this Gist for unit tests. You can run the tests by simply copying the code from the Gist into your browser JS console and pressing enter.
Be sure to read strange JS from the internet before blindly pasting it into your console.
https://gist.github.com/angstyloop/504414aba95b61b98be0db580cb2a3b0
I know this is an old question but for me the only thing that worked was:
parentOfTheElement.innerHTML = parentOfTheElement.innerHTML;
While the other solutions do in fact remove all the listeners, I had problems adding new ones when using either the outerHTML trick or cloneNode()
May be the browser will do it for you if you do something like:
Copy the div and its attributes and insert it before the old one, then move the content from the old to the new and delete the old?
One method is to add a new event listener that calls e.stopImmediatePropagation().
var div = getElementsByTagName('div')[0]; /* first div found; you can use getElementById for more specific element */
div.onclick = null; // OR:
div.onclick = function(){};
//edit
I didn't knew what method are you using for attaching events. For addEventListener you can use this:
div.removeEventListener('click',functionName,false); // functionName is the name of your callback function
more details
I need to call a function at the end of a few events. So let's say I have 9 click listeners, 10 bluer listeners, some key up/down listeners etc.
A solution would be to modify all and add the function call.
But this is... well... lame.
Is there anyway I can add that call on all events at once (and any future defined events)?
Maybe extend events somehow?
Misinterpreted the question. I'm leaving this answer here as a reference, although it doesn't trigger on all events.
I would use promises for this. i.e: using Q and an event counter:
var deferred = Q.defer();
...
var allEventsRequired = { ev1 : false, ev2: false };
function tryToResolvePromise() {
for(var k in allEventsRequired){
if( !allEventsRequired[k] ) return;
}
deferred.resolve();
}
...
function markEventAsFired(name) {
allEventsRequired[name] = true;
tryToResolvePromise();
}
...
deferred.promise.then(function() { ... this will trigger when all events got fired ... } );
Call markEventAsFired( name ) from where each of your events are firing. And if you need any new one in the future just add it's name to the map allEventsRequired. Don't forget to initialize them as false.
I always wondered how clean is such approach - to remove an event listener from within that very listener.
UPDATE:
Internally I keep a hash of objects and listeners, so I potentially can remove event listener from any place. I'm just concerned of removing it from within itself. Will such action do a job actually?
UPDATE
I'm asking about addEventListener, removeEventListener stuff.
You can pass the once option to have a listener act only once, then remove itself. Docs: https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#Parameters
Example:
element.addEventListener('eventname', (ev) => {
console.log("event is captured only once.");
// do more stuff...
}, { once: true });
From the same docs link above, modern browser support is good, but is not available for Internet Explorer.
I just saw this because i wondered the exact same question!
arguments.callee is your friend...
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Functions_and_function_scope/arguments/callee
so you'd have
blah.addEventListener('click',function(e){
e.source.removeEventListener('click', arguments.callee);
blee bloo bleep
});
this works in Titanium Appcelerator, so it should work in javascript too (because they are The Same Thing Kinda)
NB do NOT add () to the end of arguments.callee in this example, unless you like seeing... bah dum tish!.
In fact, if you don't want to use arguments.callee, this also might work (untested):
blah.addEventListener('click', anyThingYouWantHere = function(e){
e.source.removeEventListener('click', anyThingYouWantHere);
blee bloo bleep
});
Where "anythingYouWantHere" is any variable name you'd like ~ you're effectively "naming" the function as you add it.
I just made a wrapper function that generates a self destructing event listener:
let addSelfDestructingEventListener = (element, eventType, callback) => {
let handler = () => {
callback();
element.removeEventListener(eventType, handler);
};
element.addEventListener(eventType, handler);
};
So far it works great :)
#bharal answer gave me now this solution:
//example
addBlurListener(element, field) {
const listenToBlur = (e) => {
e.target.removeEventListener(e.type, listenToBlur);
//your stuff
};
element.addEventListener('blur', listenToBlur);
},
You could try something like this, depending on how it's called:
some_div.onclick = function () {
...
this.onclick = null;
// or: some_div.onclick = null;
};
Or is it event listeners you're concerned with? Because those are a little bit more complicated.
If you want listener only trigger once, you can use this code:
element.addEventListener('eventname', function callback(){}, { once: true });
Or use wrapper to do the same thing:
function addOneTimeEventListener(element, event, callback) {
const wrapper = e => {
try {callback(e)} finally {
element.removeEventListener(event, wrapper);
};
}
element.addEventListener(event, wrapper);
}
// example
addOneTimeEventListener(document.body, 'click', e => {
console.log('this message only show once.');
});
If you want to decide when to remove listener:
function addEventListener(element, event, callback) {
const wrapper = e => {
callback(e, () => element.removeEventListener(event, wrapper));
}
element.addEventListener(event, wrapper);
}
// example
let count = 0;
addEventListener(document.body, 'click', (e, closeListener) => {
console.log(`click:${++count}`);
if(count == 3) closeListener();
});
If you use jQuery, you will probably have some convenience methods exposed for interacting with event handlers -- see bind()/unbind(), delegate()/undelegate(), one(), and similar methods.
I don't have much experience with other frameworks, but I'd imagine they offer similar functionality. If you're not using a framework at all, #sdleihssirhc has an acceptable answer.
EDIT: Ah, perhaps you're looking for something more like addEventListener() and removeEventListener(). Again, a framework will offer some convenience to your interactions and save you the trouble of reinventing the wheel in some cases.
Just question: Is there any way to completely remove all events of an object, e.g. a div?
EDIT: I'm adding per div.addEventListener('click',eventReturner(),false); an event.
function eventReturner() {
return function() {
dosomething();
};
}
EDIT2: I found a way, which is working, but not possible to use for my case:
var returnedFunction;
function addit() {
var div = document.getElementById('div');
returnedFunction = eventReturner();
div.addEventListener('click',returnedFunction,false); //You HAVE to take here a var and not the direct call to eventReturner(), because the function address must be the same, and it would change, if the function was called again.
}
function removeit() {
var div = document.getElementById('div');
div.removeEventListener('click',returnedFunction,false);
}
I am not sure what you mean with remove all events. Remove all handlers for a specific type of event or all event handlers for one type?
Remove all event handlers
If you want to remove all event handlers (of any type), you could clone the element and replace it with its clone:
var clone = element.cloneNode(true);
Note: This will preserve attributes and children, but it will not preserve any changes to DOM properties.
Remove "anonymous" event handlers of specific type
The other way is to use removeEventListener() but I guess you already tried this and it didn't work. Here is the catch:
Calling addEventListener to an anonymous function creates a new listener each time. Calling removeEventListener to an anonymous function has no effect. An anonymous function creates a unique object each time it is called, it is not a reference to an existing object though it may call one. When adding an event listener in this manner be sure it is added only once, it is permanent (cannot be removed) until the object it was added to, is destroyed.
You are essentially passing an anonymous function to addEventListener as eventReturner returns a function.
You have two possibilities to solve this:
Don't use a function that returns a function. Use the function directly:
function handler() {
dosomething();
}
div.addEventListener('click',handler,false);
Create a wrapper for addEventListener that stores a reference to the returned function and create some weird removeAllEvents function:
var _eventHandlers = {}; // somewhere global
const addListener = (node, event, handler, capture = false) => {
if (!(event in _eventHandlers)) {
_eventHandlers[event] = []
}
// here we track the events and their nodes (note that we cannot
// use node as Object keys, as they'd get coerced into a string
_eventHandlers[event].push({ node: node, handler: handler, capture: capture })
node.addEventListener(event, handler, capture)
}
const removeAllListeners = (targetNode, event) => {
// remove listeners from the matching nodes
_eventHandlers[event]
.filter(({ node }) => node === targetNode)
.forEach(({ node, handler, capture }) => node.removeEventListener(event, handler, capture))
// update _eventHandlers global
_eventHandlers[event] = _eventHandlers[event].filter(
({ node }) => node !== targetNode,
)
}
And then you could use it with:
addListener(div, 'click', eventReturner(), false)
// and later
removeAllListeners(div, 'click')
DEMO
Note: If your code runs for a long time and you are creating and removing a lot of elements, you would have to make sure to remove the elements contained in _eventHandlers when you destroy them.
This will remove all listeners from children but will be slow for large pages. Brutally simple to write.
element.outerHTML = element.outerHTML;
Use the event listener's own function remove(). For example:
getEventListeners().click.forEach((e)=>{e.remove()})
As corwin.amber says, there are differences between Webkit an others.
In Chrome:
getEventListeners(document);
Which gives you an Object with all the existing event listeners:
Object
click: Array[1]
closePopups: Array[1]
keyup: Array[1]
mouseout: Array[1]
mouseover: Array[1]
...
From here you can reach the listener you want to remove:
getEventListeners(document).copy[0].remove();
So All the event listeners:
for(var eventType in getEventListeners(document)) {
getEventListeners(document)[eventType].forEach(
function(o) { o.remove(); }
)
}
In Firefox
Is a little bit different because it uses a listener wrapper that contains no remove function. You have to get the listener you want to remove:
document.removeEventListener("copy", getEventListeners(document).copy[0].listener)
All the event listeners:
for(var eventType in getEventListeners(document)) {
getEventListeners(document)[eventType].forEach(
function(o) { document.removeEventListener(eventType, o.listener) }
)
}
I stumbled with this post trying to disable the annoying copy protection of a news website.
Enjoy!
You can add a hook function to intercept all calls to addEventHandler. The hook will push the handler to a list that can be used for cleanup. For example,
if (EventTarget.prototype.original_addEventListener == null) {
EventTarget.prototype.original_addEventListener = EventTarget.prototype.addEventListener;
function addEventListener_hook(typ, fn, opt) {
console.log('--- add event listener',this.nodeName,typ);
this.all_handlers = this.all_handlers || [];
this.all_handlers.push({typ,fn,opt});
this.original_addEventListener(typ, fn, opt);
}
EventTarget.prototype.addEventListener = addEventListener_hook;
}
You should insert this code near the top of your main web page (e.g. index.html). During cleanup, you can loop thru all_handlers, and call removeEventHandler for each. Don't worry about calling removeEventHandler multiple times with the same function. It is harmless.
For example,
function cleanup(elem) {
for (let t in elem) if (t.startsWith('on') && elem[t] != null) {
elem[t] = null;
console.log('cleanup removed listener from '+elem.nodeName,t);
}
for (let t of elem.all_handlers || []) {
elem.removeEventListener(t.typ, t.fn, t.opt);
console.log('cleanup removed listener from '+elem.nodeName,t.typ);
}
}
Note: for IE use Element instead of EventTarget, and change => to function, and various other things.
Clone the element and replace the element with its clone. Events are not cloned.
elem.replaceWith(elem.cloneNode(true));
This uses Node.cloneNode() to clone the elem DOM object, which ignores all event handlers (though, as Jan Turoň's answer notes, attributes like onclick="…" will remain). It then uses Element.replaceWith() to replace elem with that clone. Simple assignment to an anonymous clone wasn't working for me.
This should be faster and cleaner than redefining elem.outerHTML with itself (as proposed by pabombs's answer) but may be slower than answers that iterate through and purge each listener (noting that getEventListeners() seems available exclusively in Chrome's dev console—not elsewhere in Chrome, not at all on Firefox). Presumably, at some higher volume of listeners to clear, this non-loop solution becomes faster.
(This is a simplification of Felix Kling's answer with help from asheroto's comment to it.)
you can add function and remove all other click by assign them
btn1 = document.querySelector(".btn-1")
btn1.addEventListener("click" , _=>{console.log("hello")})
btn1.addEventListener("click" , _=>{console.log("How Are you ?")})
btn2 = document.querySelector(".btn-2")
btn2.onclick = _=>{console.log("Hello")}
btn2.onclick = _=>{console.log("Bye")}
<button class="btn-1">Hello to Me</button>
<button class="btn-2">Hello to Bye</button>
You can indeed remove all event handlers by cloning the node as #FelixKling suggests in his answer, however don't forget that
attribute event handlers are not affected by cloning
Having element like this
<div id="test" onclick="alert(42)">test</div>
will still alert on click after cloning. To remove this sort of events, you need to use removeAttribute method, in general
const removeAttEvents = el =>
[...el.attributes].forEach(att =>
att.name.startsWith("on") && el.removeAttribute(att.name)
);
Then having the test element above, calling removeAttEvents(test) gets rid of the click handler.
To complete the answers, here are real-world examples of removing events when you are visiting websites and don't have control over the HTML and JavaScript code generated.
Some annoying websites are preventing you to copy-paste usernames on login forms, which could easily be bypassed if the onpaste event was added with the onpaste="return false" HTML attribute.
In this case we just need to right click on the input field, select "Inspect element" in a browser like Firefox and remove the HTML attribute.
However, if the event was added through JavaScript like this:
document.getElementById("lyca_login_mobile_no").onpaste = function(){return false};
We will have to remove the event through JavaScript also:
document.getElementById("lyca_login_mobile_no").onpaste = null;
In my example, I used the ID "lyca_login_mobile_no" since it was the text input ID used by the website I was visiting.
Another way to remove the event (which will also remove all the events) is to remove the node and create a new one, like we have to do if addEventListener was used to add events using an anonymous function that we cannot remove with removeEventListener.
This can also be done through the browser console by inspecting an element, copying the HTML code, removing the HTML code and then pasting the HTML code at the same place.
It can also be done faster and automated through JavaScript:
var oldNode = document.getElementById("lyca_login_mobile_no");
var newNode = oldNode.cloneNode(true);
oldNode.parentNode.insertBefore(newNode, oldNode);
oldNode.parentNode.removeChild(oldNode);
Update: if the web app is made using a JavaScript framework like Angular, it looks the previous solutions are not working or breaking the app.
Another workaround to allow pasting would be to set the value through JavaScript:
document.getElementById("lyca_login_mobile_no").value = "username";
At the moment, I don't know if there is a way to remove all form validation and restriction events without breaking an app written entirely in JavaScript like Angular.
Update 2: There is also a way to remove a specific event that was added with addEventListener on a website we don't own, by using the getEventListeners function combined to removeEventListener like mentioned in the answer of Jmakuc. If getEventListeners does not exist like on Firefox, you can use a polyfill and inject the script on the page with Greasemonkey addon: https://github.com/colxi/getEventListeners/issues/1
The only easy way I found and worked is this:
Let's say we want to add 2 event listeners
const element = document.getElementById("element");
element.addEventListener('mouseover',
()=>{
// some task
});
element.addEventListener('mouseout',
()=>{
// some task
});
Now you can remove both of the elements by simply:
element.replaceWith(element.cloneNode(true));
Removing all the events on document:
One liner:
for (key in getEventListeners(document)) { getEventListeners(document)[key].forEach(function(c) { c.remove() }) }
Pretty version:
for (key in getEventListeners(document)) {
getEventListeners(document)[key].forEach(function(c) {
c.remove()
})
}
angular has a polyfill for this issue, you can check. I did not understand much but maybe it can help.
const REMOVE_ALL_LISTENERS_EVENT_LISTENER = 'removeAllListeners';
proto[REMOVE_ALL_LISTENERS_EVENT_LISTENER] = function () {
const target = this || _global;
const eventName = arguments[0];
if (!eventName) {
const keys = Object.keys(target);
for (let i = 0; i < keys.length; i++) {
const prop = keys[i];
const match = EVENT_NAME_SYMBOL_REGX.exec(prop);
let evtName = match && match[1];
// in nodejs EventEmitter, removeListener event is
// used for monitoring the removeListener call,
// so just keep removeListener eventListener until
// all other eventListeners are removed
if (evtName && evtName !== 'removeListener') {
this[REMOVE_ALL_LISTENERS_EVENT_LISTENER].call(this, evtName);
}
}
// remove removeListener listener finally
this[REMOVE_ALL_LISTENERS_EVENT_LISTENER].call(this, 'removeListener');
}
else {
const symbolEventNames = zoneSymbolEventNames$1[eventName];
if (symbolEventNames) {
const symbolEventName = symbolEventNames[FALSE_STR];
const symbolCaptureEventName = symbolEventNames[TRUE_STR];
const tasks = target[symbolEventName];
const captureTasks = target[symbolCaptureEventName];
if (tasks) {
const removeTasks = tasks.slice();
for (let i = 0; i < removeTasks.length; i++) {
const task = removeTasks[i];
let delegate = task.originalDelegate ? task.originalDelegate : task.callback;
this[REMOVE_EVENT_LISTENER].call(this, eventName, delegate, task.options);
}
}
if (captureTasks) {
const removeTasks = captureTasks.slice();
for (let i = 0; i < removeTasks.length; i++) {
const task = removeTasks[i];
let delegate = task.originalDelegate ? task.originalDelegate : task.callback;
this[REMOVE_EVENT_LISTENER].call(this, eventName, delegate, task.options);
}
}
}
}
if (returnTarget) {
return this;
}
};
....
You can add a helper function that clears event listener for example
function clearEventListener(element) {
const clonedElement = element.cloneNode(true);
element.replaceWith(clonedElement);
return clonedElement;
}
just pass in the element to the function and that's it...
Sub-class of EventTarget from the JavaScript WebAPI. Supports removing events without specifying a handler function reference.
class SmartEventTarget extends EventTarget {
constructor() {
super();
this.handlers = {};
}
addEventListener(name, handler) {
super.addEventListener(name, handler);
if (!this.handlers[name]) {
this.handlers[name] = new Set();
}
this.handlers[name].add(handler);
}
removeEventListener(name, handler) {
if (handler) {
super.removeEventListener(name, handler);
this.handlers[name].delete(handler);
} else {
this.handlers[name].forEach(h => {
super.removeEventListener(name, h)
});
this.handlers[name].clear();
}
}
removeAllListeners(name) {
if (name) {
this.removeEventListener(name, null);
} else {
Object.keys(this.handlers).map(name => {
this.removeEventListener(name, null);
});
this.handlers = {};
}
}
}
See this Gist for unit tests. You can run the tests by simply copying the code from the Gist into your browser JS console and pressing enter.
Be sure to read strange JS from the internet before blindly pasting it into your console.
https://gist.github.com/angstyloop/504414aba95b61b98be0db580cb2a3b0
I know this is an old question but for me the only thing that worked was:
parentOfTheElement.innerHTML = parentOfTheElement.innerHTML;
While the other solutions do in fact remove all the listeners, I had problems adding new ones when using either the outerHTML trick or cloneNode()
May be the browser will do it for you if you do something like:
Copy the div and its attributes and insert it before the old one, then move the content from the old to the new and delete the old?
One method is to add a new event listener that calls e.stopImmediatePropagation().
var div = getElementsByTagName('div')[0]; /* first div found; you can use getElementById for more specific element */
div.onclick = null; // OR:
div.onclick = function(){};
//edit
I didn't knew what method are you using for attaching events. For addEventListener you can use this:
div.removeEventListener('click',functionName,false); // functionName is the name of your callback function
more details