How can I add an event listener for all events in javascript without listing them individually?

Question

I'd like to accomplish the following code using a wildcard (that I don't think exists?)

myObject.element = document.getElementsByClassName('js-myObject');
myObject.element.addEventListener('click', myObject.click);
myObject.element.addEventListener('mouseover', myObject.mouseover);
//etc..

So far, I have the following

myObject.controller = function(e){
   if( (e.type in myObject) && (typeof myObject[e.type] ==='function') ){
      myObject[e.type](e);
   }
};

//but the listeners still have to be assigned as such
myObject.element = document.getElementsByClassName('js-myObject');
myObject.element.addEventListener('click', myObject.controller);
myObject.element.addEventListener('mouseover', myObject.controller);
//etc...


// but I want to do (and it doesn't work)
myObject.element.addEventListener('*', myObject.controller);

Any suggestions on methods other than an array of events and a foreach statement?

Edit, my current solution

I've accepted an answer below (there's no wildcard available, and it's a bad idea to parse potentially hundreds of events)

For those looking for a similar function, I've settled on the following approach, at least for now.

for(var prop in myObject){
  if (!myObject.hasOwnProperty(prop){continue;}
  if (typeof myObject[prop] !== 'function'){continue;}
  myObject.element.addEventListener(prop, myObject[prop]);
}

The upside is a handler for custom events that I don't have to go back and add listeners for. The downside is that I have to ensure this function is called after every myObject.someEvent() is defined. I call it in myObject.init(); which works for me just fine. Note that this solution wouldn't fit my previous specs, because it uses a for/each loop -- but it accomplishes what i really wanted to accomplish and a big thanks to @torazaburo for clearly defining the technical limitations and lack of wisdom in my initial plan.

Answer 1

How to implement addEventListener('*') yourself

For all native events, we can retrieve a list of supported events by iterating over the target.onevent properties and installing our listener for all of them.

for (const key in target) {
    if(/^on/.test(key)) {
        const eventType = key.substr(2);
        target.addEventListener(eventType, listener);
    }
}

The only other way that events are emitted which I know of is via EventTarget.dispatchEvent, which every Node and thefore every Element inherits.
To listen for all these manually triggered events, we can proxy the dispatchEvent method globally and install our listener just-in-time for the event whose name we just saw ✨ ^^

const dispatchEvent_original = EventTarget.prototype.dispatchEvent;
EventTarget.prototype.dispatchEvent = function (event) {
    if (!alreadyListenedEventTypes.has(event.type)) {
        target.addEventListener(event.type, listener, ...otherArguments);
        alreadyListenedEventTypes.add(event.type);
    }
    dispatchEvent_original.apply(this, arguments);
};

function snippet

function addEventListenerAll(target, listener, ...otherArguments) {

    // install listeners for all natively triggered events
    for (const key in target) {
        if (/^on/.test(key)) {
            const eventType = key.substr(2);
            target.addEventListener(eventType, listener, ...otherArguments);
        }
    }

    // dynamically install listeners for all manually triggered events, just-in-time before they're dispatched ;D
    const dispatchEvent_original = EventTarget.prototype.dispatchEvent;
    function dispatchEvent(event) {
        target.addEventListener(event.type, listener, ...otherArguments);  // multiple identical listeners are automatically discarded
        dispatchEvent_original.apply(this, arguments);
    }
    EventTarget.prototype.dispatchEvent = dispatchEvent;
    if (EventTarget.prototype.dispatchEvent !== dispatchEvent) throw new Error(`Browser is smarter than you think!`);

}


// usage example
function addEventListenerAll(target, listener, ...otherArguments) {

    // install listeners for all natively triggered events
    for (const key in target) {
        if (/^on/.test(key)) {
            const eventType = key.substr(2);
            target.addEventListener(eventType, listener, ...otherArguments);
        }
    }

    // dynamically install listeners for all manually triggered events, just-in-time before they're dispatched ;D
    const dispatchEvent_original = EventTarget.prototype.dispatchEvent;
    function dispatchEvent(event) {
        target.addEventListener(event.type, listener, ...otherArguments);  // multiple identical listeners are automatically discarded
        dispatchEvent_original.apply(this, arguments);
    }
    EventTarget.prototype.dispatchEvent = dispatchEvent;
    if (EventTarget.prototype.dispatchEvent !== dispatchEvent) throw new Error(`Browser is smarter than you think!`);

}


// usage example
addEventListenerAll(window, (evt) => {
    console.log(evt.type);
});
document.body.click();
document.body.dispatchEvent(new Event('omg!', { bubbles: true }));


// usage example with `useCapture`
// (also receives `bubbles: false` events, but in reverse order)
addEventListenerAll(
    window,
    (evt) => { console.log(evt.type); },
    true
);
document.body.dispatchEvent(new Event('omfggg!', { bubbles: false }));

Answer 2

A little late to the party, but here's how I add all event listeners & log them to the console:

Object.keys(window).forEach(key => {
    if(/./.test(key)){
        window.addEventListener(key.slice(2), event => {
            console.log(key, event)
        })
    }
})

Answer 3

There's no wild card, but using jQuery you can have 1 long event listener line, rather than multiple.

How do you log all events fired by an element in jQuery?

Like so:

('body').on("click mousedown mouseup focus blur keydown change dblclick mousemove mouseover mouseout mousewheel keydown keyup keypress textInput touchstart touchmove touchend touchcancel resize scroll zoom select change submit reset",function(e){
     console.log(e);
}); 

Answer 4

There is no feature to add a * listener, and I doubt if you want hundreds of events on an element being listened for anyway.

By the way, instead of your roll-your-own architecture for a generic event handler in the form of your myObject.controller, you should use the under-appreciated approach involving the EventListener interface and the handleEvent method it defines.

Answer 5

I'm not a 100% if this is what you're looking for, but I think this is what you're looking for.

the document which is what we usually tag into for our events doesn't contain the events. It's actually the grandparent class.

document -> HTMLDocument -> Document (where you could find the onclick* events)

as you could see we can then do this. just trim the on at the start of the events

Object.keys(document.__proto__.__proto__).reduce((arr, event)=> {
  if(event.startsWith('on')) return [...arr, event.substr(2)];
  return arr;
}, [])

which would return something like:

["readystatechange", "pointerlockchange", "pointerlockerror", "beforecopy", "beforecut", "beforepaste", "freeze", "resume", "search", "securitypolicyviolation", "visibilitychange", "copy", "cut", "paste", "abort", "blur", "cancel", "canplay", "canplaythrough", "change", "click", "close", "contextmenu", "cuechange", "dblclick", "drag", "dragend", "dragenter", "dragleave", "dragover", "dragstart", "drop", "durationchange", "emptied", "ended", "error", "focus", "formdata", "input", "invalid", "keydown", "keypress", "keyup", "load", "loadeddata", "loadedmetadata", "loadstart", "mousedown", "mouseenter", "mouseleave", "mousemove", "mouseout", "mouseover", "mouseup", "mousewheel", "pause", "play", "playing", "progress", "ratechange", "reset", "resize", "scroll", "seeked", "seeking", "select", "stalled", "submit", "suspend", "timeupdate", "toggle", "volumechange", "waiting", "webkitanimationend", "webkitanimationiteration", "webkitanimationstart", "webkittransitionend", "wheel", "auxclick", "gotpointercapture", "lostpointercapture", "pointerdown", "pointermove", "pointerup", "pointercancel", "pointerover", "pointerout", "pointerenter", "pointerleave", "selectstart", "selectionchange", "animationend", "animationiteration", "animationstart", "transitionend", "fullscreenchange", "fullscreenerror", "webkitfullscreenchange", "webkitfullscreenerror", "pointerrawupdate"]

this is just something quick I came up with and I'm sure there are better answers from smarter folks. you might also want to check out https://developer.mozilla.org/en-US/docs/Web/Events which contains what you just might need.

Answer 6

To find all event listeners on the page

getEventListeners(document)

Reference

To list them a little nicer

for (const [key, value] of Object.entries(getEventListeners(document))) {
      console.log(`${key}`) 
}

I will leave it up to you to actually do something with each, but now you can at least see all that exist on the page, you can open DevTools and try it out on this page and see for yourself it does work.

Answer 7

getElementsByClassName already returns an array (or more specifically, an HTMLCollection), not a single element. Just do it in a loop.

myObject.element = document.getElementsByClassName('js-myObject');
for(var i=0; i<myObject.element.length; i++){
    myObject.element[i].addEventListener('click', myObject.controller);
    myObject.element[i].addEventListener('mouseover', myObject.controller);
}

Edit... after clarification.. loops and arrays are still useful

var e = ['click', 'hover', 'focus', 'mouseover', 'mouseout'];
myObject.element = document.getElementsByClassName('js-myObject');
for(var i=0; i<myObject.element.length; i++){
    for(var n=0; n<e.length; n++)
        myObject.element[i].addEventListener(e[n], myObject.controller);
}

Answer 8

Something like this ?

        document.addEventListener('click', function (event) {

            if (event.target.closest('.scroll')) {
                // Do something...
            }

            if (event.target.matches('[data-some-attribute]')) {
                // Do something else...
            }

            if (event.target.matches('#my-form')) {
                // Do another t hing...
            }

        }, false)