element.addEventListener

BaselineWidely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

* Some parts of this feature may have varying levels of support.

Resumen

addEventListener() Registra un evento a un objeto en específico. ElObjeto especifico puede ser un simpleelemento en un archivo, el mismodocumento , unaventana o unXMLHttpRequest.

Para registrar más de un eventListener, puedes llamaraddEventListener() para el mismo elemento pero con diferentes tipos de eventos o parámetros de captura.

Sintaxis

target.addEventListener(tipo, listener[, useCapture]);target.addEventListener(tipo, listener[, useCapture, wantsUntrustedNo estándar]); // Gecko/Mozilla only

tipo: Una cadena representando eltipo de evento a escuchar.
listener: El objeto que recibe una notificación cuando un evento de el tipo especificado ocurre. Debe ser un objeto implementando la interfazEventListener o solo unafunction en JavaScript.
useCaptureOpcional: Si estrue,useCapture indica que el usuario desea iniciar la captura. Después de iniciar la captura, todos los eventos del tipo especificado serán lanzados allistener registrado antes de comenzar a ser controlados por algúnEventTarget que esté por debajo en el arbol DOM del documento.
Nota:For event listeners attached to the event target; the event is in the target phase, rather than capturing and bubbling phases. Events in the target phase will trigger all listeners on an element regardless of theuseCapture parameter.
Nota:useCapture became optional only in more recent versions of the major browsers; for example, it was not optional prior to Firefox 6. You should provide that parameter for broadest compatibility.

wantsUntrusted No estándar: Iftrue, the listener receives synthetic events dispatched by web content (the default isfalse for chrome andtrue for regular web pages). This parameter is only available in Gecko and is mainly useful for the code in add-ons and the browser itself. SeeInteraction between privileged and non-privileged pages for an example.

En el ejemplo anterior ,modifyText() es una listener para los eventosclick registrados utilzandoaddEventListener(). Un click en cualquier parte de la tabla notificara al handler y ejecutara la funciónmodifyText().

Si quieres pasar parámetros a la función del listener, debes utilizar funciones anónimas.

html

<!doctype html><html>  <head>    <title>DOM Event Example</title>    <style>      #t {        border: 1px solid red;      }      #t1 {        background-color: pink;      }    </style>    <script>      // Function to change the content of t2      function modifyText(new_text) {        var t2 = document.getElementById("t2");        t2.firstChild.nodeValue = new_text;      }      // Function to add event listener to t      function load() {        var el = document.getElementById("t");        el.addEventListener(          "click",          function () {            modifyText("four");          },          false,        );      }    </script>  </head>  <body onload="load();">    <table>      <tr>        <td>one</td>      </tr>      <tr>        <td>two</td>      </tr>    </table>  </body></html>

Notas

¿Porqué utilizar`addEventListener`?

addEventListener es la forma de registrar un listener de eventos, como se especifica en W3C DOM. Sus beneficios son los siguientes:

Permite agregar mas de un listener a un solo evento. Esto es particularmente útil para las libreriasDHTML o lasExtensiones de Mozilla que deben funcionar bien, incluso si se utilizan otras librerias/extensiones.
Da un control mas detallado de la fase en la que el listener se activa (capturing vs. bubbling)
Funciona en cualquier elemento del DOM, no únicamente con elementos de HTML.

La alternativa,Antigua forma de registrar event listeners es descrita a continuación.

Adding a listener during event dispatch

If anEventListener is added to anEventTarget while it is processing an event, it will not be triggered by the current actions but may be triggered during a later stage of event flow, such as the bubbling phase.

Multiple identical event listeners

If multiple identicalEventListeners are registered on the sameEventTarget with the same parameters, the duplicate instances are discarded. They do not cause theEventListener to be called twice, and since the duplicates are discarded, they do not need to be removed manually with theremoveEventListener method.

The value of`this` within the handler

It is often desirable to reference the element from which the event handler was fired, such as when using a generic handler for a series of similar elements. When attaching a function usingaddEventListener() the value ofthis is changed—note that the value ofthis is passed to a function from the caller.

In the example above, the value ofthis withinmodifyText() when called from the click event is a reference to the table 't'. This is in contrast to the behavior that occurs if the handler is added in the HTML source:

html

<table>  . . .</table>

The value ofthis withinmodifyText() when called from the onclick event will be a reference to the global (window) object.

Nota:JavaScript 1.8.5 introduces theFunction.prototype.bind() method, which lets you specify the value that should be used asthis for all calls to a given function. This lets you easily bypass problems where it's unclear what this will be, depending on the context from which your function was called. Note, however, that you'll need to keep a reference to the listener around so you can later remove it.

This is an example with and withoutbind:

var Something = function (element) {  this.name = "Something Good";  this.onclick1 = function (event) {    console.log(this.name); // undefined, as this is the element  };  this.onclick2 = function (event) {    console.log(this.name); // 'Something Good', as this is the binded Something object  };  element.addEventListener("click", this.onclick1, false);  element.addEventListener("click", this.onclick2.bind(this), false); // Trick};

A problem in the example above is that you cannot remove the listener withbind. Another solution is using a special function calledhandleEvent to catch any events:

var Something = function (element) {  this.name = "Something Good";  this.handleEvent = function (event) {    console.log(this.name); // 'Something Good', as this is the Something object    switch (event.type) {      case "click":        // some code here...        break;      case "dblclick":        // some code here...        break;    }  };  // Note that the listeners in this case are this, not this.handleEvent  element.addEventListener("click", this, false);  element.addEventListener("dblclick", this, false);  // You can properly remove the listners  element.removeEventListener("click", this, false);  element.removeEventListener("dblclick", this, false);};

Legacy Internet Explorer and attachEvent

In Internet Explorer versions prior to IE 9, you have to useattachEvent rather than the standardaddEventListener. To support IE, the example above can be modified to:

if (el.addEventListener) {  el.addEventListener("click", modifyText, false);} else if (el.attachEvent) {  el.attachEvent("onclick", modifyText);}

There is a drawback toattachEvent, the value ofthis will be a reference to thewindow object instead of the element on which it was fired.

Older way to register event listeners

addEventListener() was introduced with the DOM 2Events specification. Before then, event listeners were registered as follows:

// Pass a function reference — do not add '()' after it, which would call the function!el.onclick = modifyText;// Using a function expressionelement.onclick = function () {  // ... function logic ...};

This method replaces the existingclick event listener(s) on the element if there are any. Similarly for other events and associated event handlers such asblur (onblur),keypress (onkeypress), and so on.

Because it was essentially part of DOM 0, this method is very widely supported and requires no special cross–browser code; hence it is normally used to register event listeners dynamically unless the extra features ofaddEventListener() are needed.

Memory issues

var i;var els = document.getElementsByTagName('*');// Case 1for(i=0 ; i<els.length ; i++){  els[i].addEventListener("click", function(e){/*do something*/}, false});}// Case 2function processEvent(e){  /*do something*/}for(i=0 ; i<els.length ; i++){  els[i].addEventListener("click", processEvent, false});}

In the first case, a new (anonymous) function is created at each loop turn. In the second case, the same previously declared function is used as an event handler. This results in smaller memory consumption. Moreover, in the first case, since no reference to the anonymous functions is kept, it is not possible to callelement.removeEventListener because we do not have a reference to the handler, while in the second case, it's possible to domyElement.removeEventListener("click", processEvent, false).

Especificaciones

Specification
DOM # ref-for-dom-eventtarget-addeventlistener③

Compatibilidad con navegadores

Help improve MDN

Was this page helpful to you?

Learn how to contribute.

This page was last modified on24 jun 2025 byMDN contributors.

View this page on GitHub •Report a problem with this content

Movatterモバイル変換

En este artículo