javascripteventsdom

How to remove all event listeners of a DOM object in JavaScript?


Is there any way to completely remove all events of an object, e.g. a div?

I'm adding per div.addEventListener('click',eventReturner(),false); an event.

function eventReturner() {
    return function() {
        dosomething();
    };
}

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();
    // 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.
    div.addEventListener('click',returnedFunction,false);
}
function removeit() {
    var div = document.getElementById('div');
    div.removeEventListener('click',returnedFunction,false);
}

Solution

  • 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:

    1. Don't use a function that returns a function. Use the function directly:

       function handler() {
           dosomething();
       }
      
       div.addEventListener('click',handler,false);
      
    2. 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.