DOM events

Events are fired to notify code of "interesting changes" that may affect code execution. These can arise from user interactions such as using a mouse or resizing a window, changes in the state of the underlying environment (e.g., low battery or media events from the operating system), and other causes.

Each event is represented by an object that is based on the Event interface, and may have additional custom fields and/or functions to provide information about what happened. The documentation for every event has a table (near the top) that includes a link to the associated event interface, and other relevant information. A full list of the different event types is given in Event > Interfaces based on Event.

This topic provides an index to the main sorts of events you might be interested in (animation, clipboard, workers etc.) along with the main classes that implement those sorts of events.

Event index

Event type	Description	Documentation
Animation	Events related to the Web Animation API. Used to respond to changes in animation status (e.g., when an animation starts or ends).	Animation events fired on `Document`, `Window`, `HTMLElement`.
Asynchronous data fetching	Events related to the fetching data.	Events fired on `AbortSignal`, `XMLHttpRequest`, `FileReader`.
Clipboard	Events related to the Clipboard API. Used to notify when content is cut, copied, or pasted.	Events fired on `Document`, `Element`, `Window`.
Composition	Events related to composition; entering text "indirectly" (rather than using normal keyboard presses). For example, text entered via a speech to text engine, or using special key combinations that modify keyboard presses to represent new characters in another language.	Events fired on `Element`.
CSS transition	Events related to CSS Transitions. Provides notification events when CSS transitions start, stop, are cancelled, etc.	Events fired on `Document`, `HTMLElement`, `Window`.
Database	Events related to database operations: opening, closing, transactions, errors, etc.	Events fired on `IDBDatabase`, `IDBOpenDBRequest`, `IDBRequest`, `IDBTransaction`.
DOM mutation	Events related to modifications to the Document Object Model (DOM) hierarchy and nodes.	Warning: Mutation Events are deprecated. Mutation Observers should be used instead.
Drag'n'drop, Wheel	Events related to using the HTML Drag and Drop API and wheel events. Drag and Wheel events are derived from mouse events. While they are fired when using mouse wheel or drag/drop, they may also be used with other appropriate hardware.	Drag events fired on `Document` Wheel events fired on `Element`
Focus	Events related to elements gaining and losing focus.	Events fired on `Element`, `Window`.
Form	Events related to forms being constructed, reset and submitted.	Events fired on `HTMLFormElement`.
Fullscreen	Events related to the Fullscreen API. Used to notify when the transitioning between full screen and windowed modes, and also of errors occurring during this transition.	Events fired on `Document`, `Element`.
Gamepad	Events related to the Gamepad API.	Events fired on `Window`.
Gestures	Touch events are recommended for implementing gestures.	Events fired on `Document`, `Element`. In addition there are a number of non-standard gesture events: Non-standard WebKit specific events on `Element`: `gesturestart` event, `gesturechange` event, `gestureend` event.
History	Events related to the History API.	Events fired on `Window`.
HTML element content display management	Events related to changing the state of a display or textual element.	Events fired on `HTMLDetailsElement`, `HTMLDialogElement`, `HTMLSlotElement`.
Inputs	Events related to HTML input elements e.g. `<input>`, `<select>`, or `<textarea>`.	Events fired on `HTMLElement`, `HTMLInputElement`.
Keyboard	Events related to using a keyboard. Used to notify when keys are moved up, down, or just pressed.	Events fired on `Document`, `Element`.
Loading/unloading documents	Events related to loading and unloading documents.	Events fired on `Document` and `Window`.
Manifests	Events related to installation of progressive web app manifests.	Events fired on `Window`.
Media	Events related to media usage (including the Media Capture and Streams API, Web Audio API, Picture-in-Picture API, etc.).	Events fired on `ScriptProcessorNode`, `HTMLMediaElement`, `AudioTrackList`, `AudioScheduledSourceNode`, `MediaRecorder`, `MediaStream`, `MediaStreamTrack`, `VideoTrackList`, `HTMLTrackElement`, `OfflineAudioContext`, `TextTrack`, `TextTrackList`, Element/audio, Element/video.
Messaging	Events related to a window receiving a message from another browsing context.	Events fired on `Window`.
Mouse	Events related to using a computer mouse. Used to notify when the mouse is clicked, double-clicked, up and down events, right-click, movement in and out of an element, text selection, etc. Pointer events provide a hardware-agnostic alternative to mouse events. Drag and Wheel events are derived from mouse events.	Mouse events fired on `Element`
Network/Connection	Events related to gaining and losing network connection.	Events fired on `Window`. Events fired on `NetworkInformation` (Network Information API).
Payments	Events related to the Payment Request API.	Events fired on `PaymentRequest`, `PaymentResponse`.
Performance	Events related to any performance-related spec grouped into Performance APIs.	Events fired on `Performance`.
Pointer	Events related to the Pointer Events API. Provides hardware-agnostic notification from pointing devices including Mouse, Touch, pen/stylus.	Events fired on `Document`, `HTMLElement`.
Print	Events related to printing.	Events fired on `Window`.
Promise rejection	Events sent to the global script context when any JavaScript promise is rejected.	Events fired on `Window`.
Sockets	Events related to the WebSockets API.	Events fired on `WebSocket`.
SVG	Events related to SVG images.	Events fired on `SVGElement`, `SVGAnimationElement`, `SVGGraphicsElement`.
Text selection	Selection API events related to selecting text.	Event (`selectionchange`) fired on `HTMLTextAreaElement`, `HTMLInputElement`.
Touch	Events related to the Touch Events API. Provides notification events from interacting with a touch sensitive screen (i.e., using a finger or stylus). Not related to the Force Touch API.	Events fired on `Document`, `Element`.
Virtual reality	Events related to the WebXR Device API. Warning: The WebVR API (and associated `Window` events) are deprecated.	Events fired on `XRSystem`, `XRSession`, `XRReferenceSpace`.
RTC (real time communication)	Events related to the WebRTC API.	Events fired on `RTCDataChannel`, `RTCDTMFSender`, `RTCIceTransport`, `RTCPeerConnection`.
Server-sent events	Events related to the server sent events API.	Events fired on `EventSource`.
Speech	Events related to the Web Speech API.	Events fired on `SpeechSynthesisUtterance`.
Workers	Events related to the Web Workers API, Service Worker API, Broadcast Channel API, and Channel Messaging API. Used to respond to new messages and message sending errors. Service workers can also be notified of other events, including push notifications, users clicking on displayed notifications, that push subscription has been invalidated, deletion of items from the content index, etc.	Events fired on `ServiceWorkerGlobalScope`, `DedicatedWorkerGlobalScope`, `SharedWorkerGlobalScope`, `WorkerGlobalScope`, `Worker`, `BroadcastChannel`, `MessagePort`.

Creating and dispatching events

In addition to the events fired by built-in interfaces, you can also create and dispatch DOM events yourself. Such events are commonly called synthetic events, as opposed to the events fired by the browser itself.

Creating custom events

Events can be created with the Event constructor as follows:

const event = new Event("build");

// Listen for the event.
elem.addEventListener(
  "build",
  (e) => {
    /* … */
  },
  false,
);

// Dispatch the event.
elem.dispatchEvent(event);

The above code example uses the EventTarget.dispatchEvent() method.

Adding custom data – CustomEvent()

To add more data to the event object, the CustomEvent interface exists and the detail property can be used to pass custom data. For example, the event could be created as follows:

const event = new CustomEvent("build", { detail: elem.dataset.time });

This will then allow you to access the additional data in the event listener:

function eventHandler(e) {
  console.log(`The time is: ${e.detail}`);
}

Adding custom data – subclassing Event

The Event interface can also be subclassed. This is particularly useful for reuse, or for more complex custom data, or even adding methods to the event.

class BuildEvent extends Event {
  #buildTime;

  constructor(buildTime) {
    super("build");
    this.#buildTime = buildTime;
  }

  get buildTime() {
    return this.#buildTime;
  }
}

The above code example defines a BuildEvent class with a read-only property, and a fixed event type.

The event could then be created as follows:

const event = new BuildEvent(elem.dataset.time);

The additional data can then be accessed in the event listeners using the custom properties:

function eventHandler(e) {
  console.log(`The time is: ${e.buildTime}`);
}

Event bubbling

It is often desirable to trigger an event from a child element, and have an ancestor catch it; optionally, with data:

html

<form>
  <textarea></textarea>
</form>

const form = document.querySelector("form");
const textarea = document.querySelector("textarea");

// Create a new event, allow bubbling, and provide any data you want to pass to the "detail" property
const eventAwesome = new CustomEvent("awesome", {
  bubbles: true,
  detail: { text: () => textarea.value },
});

// The form element listens for the custom "awesome" event and then consoles the output of the passed text() method
form.addEventListener("awesome", (e) => console.log(e.detail.text()));

// As the user types, the textarea inside the form dispatches/triggers the event to fire, and uses itself as the starting point
textarea.addEventListener("input", (e) => e.target.dispatchEvent(eventAwesome));

Creating and dispatching events dynamically

Elements can listen for events that haven't been created yet:

html

<form>
  <textarea></textarea>
</form>

const form = document.querySelector("form");
const textarea = document.querySelector("textarea");

form.addEventListener("awesome", (e) => console.log(e.detail.text()));

textarea.addEventListener("input", function () {
  // Create and dispatch/trigger an event on the fly
  // Note: Optionally, we've also leveraged the "function expression" (instead of the "arrow function expression") so "this" will represent the element
  this.dispatchEvent(
    new CustomEvent("awesome", {
      bubbles: true,
      detail: { text: () => textarea.value },
    }),
  );
});

Triggering built-in events

This example demonstrates simulating a click (that is programmatically generating a click event) on a checkbox using DOM methods. View the example in action.

function simulateClick() {
  const event = new MouseEvent("click", {
    view: window,
    bubbles: true,
    cancelable: true,
  });
  const cb = document.getElementById("checkbox");
  const cancelled = !cb.dispatchEvent(event);

  if (cancelled) {
    // A handler called preventDefault.
    alert("cancelled");
  } else {
    // None of the handlers called preventDefault.
    alert("not cancelled");
  }
}

Registering event handlers

There are two recommended approaches for registering handlers. Event handler code can be made to run when an event is triggered by assigning it to the target element's corresponding onevent property, or by registering the handler as a listener for the element using the addEventListener() method. In either case the handler will receive an object that conforms to the Event interface (or a derived interface). The main difference is that multiple event handlers can be added (or removed) using the event listener methods.

Warning: A third approach for setting event handlers using HTML onevent attributes is not recommended! They inflate the markup and make it less readable and harder to debug. For more information see Inline event handlers.

Using onevent properties

By convention, JavaScript objects that fire events have a corresponding "onevent" properties (named by prefixing "on" to the name of the event). These properties are called to run associated handler code when the event is fired, and may also be called directly by your own code.

To set event handler code you can just assign it to the appropriate onevent property. Only one event handler can be assigned for every event in an element. If needed the handler can be replaced by assigning another function to the same property.

Below we show how to set a greet() function for the click event using the onclick property.

const btn = document.querySelector("button");

function greet(event) {
  console.log("greet:", event);
}

btn.onclick = greet;

Note that an object representing the event is passed as the first argument to the event handler. This event object either implements or is derived from the Event interface.

EventTarget.addEventListener

The most flexible way to set an event handler on an element is to use the EventTarget.addEventListener method. This approach allows multiple listeners to be assigned to an element, and for listeners to be removed if needed (using EventTarget.removeEventListener).

Note: The ability to add and remove event handlers allows you to, for example, have the same button performing different actions in different circumstances. In addition, in more complex programs cleaning up old/unused event handlers can improve efficiency.

Below we show how a greet() function can be set as a listener/event handler for the click event (you could use an anonymous function expression instead of a named function if desired). Note again that the event is passed as the first argument to the event handler.

const btn = document.querySelector("button");

function greet(event) {
  console.log("greet:", event);
}

btn.addEventListener("click", greet);

The method can also take additional arguments/options to control aspects of how the events are captured and removed. More information can be found on the EventTarget.addEventListener reference page.

Using an Abort Signal

A notable event listener feature is the ability to use an abort signal to clean up multiple event handlers at the same time.

This is done by passing the same AbortSignal to the addEventListener() call for all the event handlers that you want to be able to remove together. You can then call abort() on the controller owning the AbortSignal, and it will remove all event handlers that were added with that signal. For example, to add an event handler that we can remove with an AbortSignal:

const controller = new AbortController();

btn.addEventListener(
  "click",
  (event) => {
    console.log("greet:", event);
  },
  { signal: controller.signal },
); // pass an AbortSignal to this handler

Then the event handler created by the code above can be removed like this:

controller.abort(); // removes any/all event handlers associated with this controller

Specifications

Specification
DOM # events
HTML # events-2