Related
I am using JavaScript to iterate through a JSON associative array to add an event listener to a collection of different forms on the same page. The key of the array is the ID of the object on the page and the value is the message to appear in a confirmation box when the form is submitted.
For example ,I have a series of forms with IDs: confirm_1, confirm_2, confirm 2.
On the same page I have something like this:
<script type="application/json" id="json_data">{"confirm_1": "Are you sure?", "confirm_2": "Really?", "confirm_3": "Must you?"}</script>
<script src="confirmation.js"></script>
And this is confirmation.js:
var data = JSON.parse(document.getElementById('json_data').innerHTML);
for (var key in data) {
document.getElementById(key).addEventListener('submit', function(event) {
if (!confirm(data[key])) {
event.preventDefault();
}
});
};
The problem is that when I click the submit button on any form they are all assigned the confirmation message of the final element in the array. It's like all the previous addEventListener calls inherit the last call made.
What am I missing here?
You are facing issue because you have declared key as var datatype. Since it has function scope, it gets updated with the last value assigned to it which is confirm_3 in your case. This problem can be solved in different ways. I will now mention three ways to solve it.
If you are okay with using ES6, you could just use let instead of var to declare key variable. Since let has block scope, each loop block will have its own space for key variable.
By binding the value to the callback function.
By using Immediate Invoke function.
I have addressed all these in the example below and have commented them for readability.
var data = {
confirm_1: "Are you sure?",
confirm_2: "Really?",
confirm_3: "Must you?"
};
//Using let
/*for (let key in data) {
document
.getElementById(key)
.addEventListener("click", function (event) {
alert(data[key]);
});
}*/
//Using Bind
for (var key in data) {
document.getElementById(key).addEventListener(
"click",
function (message, event) {
alert(message);
}.bind(this, data[key])
);
}
//Using IIF (Immediate Invoking function)
/* for (var key in data) {
(function(message){
document
.getElementById(key)
.addEventListener("click", function (event) {
alert(message);
});
})(data[key]);
} */
<button id='confirm_1'>confirm_1</button>
<button id='confirm_2'>confirm_2</button>
<button id='confirm_3'>confirm_3</button>
Here is a link to my JS fiddle: https://jsfiddle.net/apasric4/v1qkmgyu/1/
function inputCheck(input) {
if (input.name==="email") {
console.log("email")
return isValidEmail
} else if (input.name==="password") {
return isValidPassword
console.log("pass")
} else if (input.name==="userName") {
return isValidUserName
console.log("user")
}
}
function isValidEmail (email) {
return /^[^#]+[#][^#.]+\.[a-z]+$/.test(email)
}
function isValidPassword(pass) {
return /^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$/.test(pass)
}
function isValidUserName(user) {
return /^[a-zA-Z0-9]+([_ -]?[a-zA-Z0-9])*$/.test(user)
}
function validation(e) {
e.preventDefault()
inputs.forEach(input=> createListener(inputCheck(input)))
}
function createListener(validator) {
return (e)=> {
const inputValue=e.target.value;
const valid=validator(inputValue)
console.log(valid)
}
}
I'm trying to create form validation using closures. I am trying to make my code as efficient as possible.
I want to loop over each input element (without selecting each individually), and apply an event listener to each one. The inputCheck function would return a validator function depending on the name attribute of each input, and the createListener function takes the value returned by inputCheck, which would be a specific type of validator, and then for testing purposes, console.log true or false.
So far, the only if branch that works in the inputCheck function is the first one associated with name attribute email. The other if branches won't work if I type values into other input elements and submit the form.
Can anyone tell me where I'm going wrong and how to improve my code?
I'm new to closures so I understand that this issue might seem relatively simple to most of you.
I can observe two things:
First, just like #VLAZ pointed out, two console.log in inputCheck are actually not executed since they are placed after return.
Second, createListener and validation are not quite right. createListener returns a function with one argument. validation forEach doesn't log anything because createListener returns a function, no function execution here.
There is another problem with the argument e of createListener. It seems like you treat it as an event, but based on your implementation, there is only one event, that is form submit event. So, I'd suggest to modify these two functions a little bit:
function validation(e) {
e.preventDefault()
inputs.forEach(input=> createListener(inputCheck(input))(input))
}
function createListener(validator) {
return (e)=> {
const inputValue=e.value;
const valid=validator(inputValue)
console.log(valid)
}
}
Then, the console prints out true or false based on the input value of each input field.
Please check whether the output is your intension or not https://jsfiddle.net/jqgbefhw/
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
Here is the validation function I created:
checkValidation: function (e) {
e.stopPropagation();
var data = $(e.target).val();
var color = (data === '') ? '#F00' : '#000';
$(e.target).css({ 'border': '1px solid ' + color });
}
This validation function is called whenever the focusout event is triggered:
events: {
'click #commentSubmit':'commentSubmitFun',
'focusout #commUserName':'checkValidation',
'focusout #commUserMsg':'checkValidation'
}
Now I want to call the same checkValidation function inside the commentSubmitFun like this:
if (userName !== '' && userComment !== '' {...} else { this.checkValidation(); }
However, how do I pass e.target into the checkValidation function?
When your commentSubmitFun is called on click, it will be passed the event as well. If you plan to call checkValidation within commentSubmitFun, you can pass the event object as an argument into your checkValidation call.
To be honest though, I would suggest refactoring your checkValidation function to take a String data as the parameter. This way, whenever you call checkValidation, you'll have to pass in the data that you're checking explicitly.
First off there are three separate concerns at play here
Checking validity of some data
Handling validation error
Invoking validation logic
In the simplest case, you get away with four functions,
function checkElementValidity($el) {
// some logic. return true or
// object describing an error.
// if valid, return false.
}
function displayValidationError($el, err) {
// logic to display it.
}
function handleChange(evt) {
// stop progagation.
var $el = $(evt.target);
var result = checkElementValidity($el);
// depending on result
displayValidationError($el);
}
function validateAllElements(){
var elems = [this.$el.find("#id-1"), this.$el.find("#id-2") ...];
var isValid = true;
elems.map(function ($el) {return {$el: $el, res: checkElementValidity($el);})
.filter(function (data) {return data.res;})
.forEach(function (data) { isValid = false;
displayValidationError(data.$el, data.res)});
return isValid;
}
Elsewhere,
events: {
'click #commentSubmit':'commentSubmitFun',
'focusout #commUserName':'handleChange',
'focusout #commUserMsg':'handleChange'
}
function commentSubmitForm(evt){
// your logic
var isValid = validateAllElements();
}
I don't use Backbone, so the code might not work as is. It does however illustrate the approach you may take. The exact implementation is upto you, you could collapse all 4 functions into one if you want. The important part is realizing there are separate concerns at play.
I agree with #wmock's answer. But I think it'd be better to add a new answer with code.
Since you already have the checkValidation function expecting an Event object e as argument, you just pass e to it to make it work. So when you need to invoke checkValidation in commentSubmitFun(), just checkValidation(e) and it should work.
commentSubmitFun: function(e) {
// e is the click event occured on #commentSubmit element
if (youNeedCheck) {
checkValidatoin(e)
}
}
But I don't think it is a good idea to use checkValidation as an event listener, which would lead to a restriction that you must pass an Event object as the only arguments to invoke the function. Actually, an event listener is designed to be triggered only when an event occurs, it is bound to the event and should not be invoked elsewhere.
You'd better take an element as a parameter like this
checkValidation: function (el) {
var data = $(el).val();
var color = (data === '') ? '#F00' : '#000';
$(el).css({ 'border': '1px solid ' + color });
}
Then you just invoke this checkValidation function whenever you need to validate something. Remember to refactor your code in events object.
events: {
// ...
'focusout #commUserName':'checkUserName'
}
checkUserName: function(e) {
checkValidation(e.target);
}
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