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How to remove obsolete callback from set event listener?


How to remove obsolete callback from set event listener?

By : MaxML
Date : October 22 2020, 08:10 AM
Does that help 1) Use canvas.off(), passing 'mouse:down' and a reference to the handler. Since you're using an anonymous function as a handler, you'll need to refactor to use a named function, or just remove all listeners altogether:
code :
const handler1 = function () {
  console.log('handler1')
}
// attach event listener
canvas.on('mouse:down', handler1)
// remove event listener
canvas.off('mouse:down', handler1)
// OR remove all 'mouse:down' listeners
canvas.off('mouse:down')
const handler1 = function () {
  console.log('handler1')
}
canvas.on('mouse:down', handler1)
console.log(canvas.__eventListeners)
// or, more specifically
console.log(canvas.__eventListeners['mouse:down'])


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Remove jQuery event listener when the handler needs to receive a callback function

Remove jQuery event listener when the handler needs to receive a callback function


By : waneed
Date : November 04 2020, 08:15 AM
seems to work fine One option is to namespace the events.
Example Here
code :
// Attach a keypress event namespaced to 'ebclose'
$(document).on("keypress.ebclose", function(e) {
  ebClose(e, mpClose)
});

// Remove the namespaced event:
$(document).off("keypress.ebclose");
$(document).on("keypress", $.proxy(ebClose, this, mpClose));

function ebClose(callback, e){
    if (e.which == 13){
        callback();
    }
}
function mpClose () {
    alert('Remove the event listener');
    $(document).off("keypress", $.proxy(ebClose, this, mpClose));
}
$(document).on("keypress", ebClose.bind(this, mpClose));

function ebClose(callback, e){
    if (e.which == 13){
        callback();
    }
}
function mpClose () {
    alert('Remove the event listener');
    $(document).off("keypress", ebClose.bind(this, mpClose));
}
how to remove event listener from this during callback

how to remove event listener from this during callback


By : Tim
Date : March 29 2020, 07:55 AM
should help you out Looks like stampX is recreated every time because you declare it inside the onreadystatechange function.
This means every addEventListener you do gets a different callback function.
Remove event listener from the inside if specified callback function

Remove event listener from the inside if specified callback function


By : Dave C
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further You have to pass .removeEventListener() a reference to the same function that you passed to .addEventListener(). One way to do that with minimal change to your existing code would be to name your (currently anonymous) function expression, then pass that function to pauseAudioAt() instead of passing the boolean:
code :
var pauseAudioAt = function(aud, seconds, listenerToRemove) {
    console.log(aud.currentTime);
    // check whether we have passed 5 minutes,
    // current time is given in seconds
    if(aud.currentTime >= seconds) {
        // pause the playback
        aud.pause();
        if (typeof listenerToRemove === "function") {
            aud.removeEventListener('timeupdate', listenerToRemove);
            showBtn();
        }
    }    
}

audio.addEventListener("timeupdate", function listener1() {
    pauseAudioAt(audio, 18, listener1);
});
How to remove event listener if callback is a parameterised arrow function

How to remove event listener if callback is a parameterised arrow function


By : user2987345
Date : March 29 2020, 07:55 AM
should help you out You can create a handler dynamically and store a reference to it in a closure. In this way it will be possible to deregister the handler using removeEventListener
code :
const createKeydownHandler = callback => event => {
    if (event.key === "Backspace" && document.activeElement.type === "select-one") {
        event.target.value = "";
        callback(event);
    }
};

let keydownHandler;

export const addEventToDropDown = (callback) => {
    keydownHandler = createKeydownHandler(callback);
    document.addEventListener("keydown", keydownHandler, true);
}

export const removeEventListner = () => {
    document.removeEventListener("keydown", keydownHandler)
}
How can I remove an event listener no matter how the callback is defined

How can I remove an event listener no matter how the callback is defined


By : Alexander Krechick
Date : March 29 2020, 07:55 AM
this will help You can NOT use an arrow function or any anonymous function directly and expect to be able to remove the listener.
To remove a listener requires you pass the EXACT SAME ARGUMENTS to removeEventListener as you passed to addEventListener but when you use an anonymous function or an arrow function you do not have access to that function so it's impossible for you to pass it into removeEventListener
code :
const anonFunc = () => { console.log("hello"); }
someElem.addEventListener('click', anonFunc);    
someElem.removeEventListener('click', anonFunc);  // same arguments
someElem.addEventListener('click', () => { console.log("hello"); });    
someElem.removeEventListener('click', ???) // you don't have a reference 
                                           // to the anon function so you
                                           // can't pass the correct arguments
                                           // to remove the listener
function ListenerManager() {
  let listeners = {};
  let nextId = 1;

  // Returns an id for the listener. This is easier IMO than
  // the normal remove listener which requires the same arguments as addListener
  this.on = (elem, ...args) => {
    (elem.addEventListener || elem.on || elem.addListener).call(elem, ...args);
    const id = nextId++;
    listeners[id] = {
      elem: elem,
      args: args,
    };
    if (args.length < 2) {
      throw new Error('too few args');
    }
    return id;
  };

  this.remove = (id) => {
    const listener = listeners[id];
    if (listener) {
      delete listener[id];
      const elem = listener.elem;
      (elem.removeEventListener || elem.removeListener).call(elem, ...listener.args);
    }
  };

  this.removeAll = () => {
    const old = listeners;
    listeners = {};
    Object.keys(old).forEach((id) => {
      const listener = old[id];
      if (listener.args < 2) {
        throw new Error('too few args');
      }
      const elem = listener.elem;
      (elem.removeEventListener || elem.removeListener).call(elem, ...listener.args);
    });
  };
}
const lm = new ListenerManager();
lm.on(saveElem, 'click', handleSave);
lm.on(newElem, 'click', handleNew);
lm.on(plusElem, 'ciick', handlePlusOne);
const id = lm.on(rangeElem, 'input', handleRangeChange);

lm.remove(id);  // remove the input event on rangeElem

lm.removeAll();  // remove events on all elements managed by this ListenerManager
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