Baseline Widely available
Note: This feature is available in Web Workers.
The Event
interface represents an event which takes place on an EventTarget
.
An event can be triggered by the user action e.g., clicking the mouse button or tapping keyboard, or generated by APIs to represent the progress of an asynchronous task. It can also be triggered programmatically, such as by calling the HTMLElement.click()
method of an element, or by defining the event, then sending it to a specified target using EventTarget.dispatchEvent()
.
There are many types of events, some of which use other interfaces based on the main Event
interface. Event
itself contains the properties and methods which are common to all events.
Many DOM elements can be set up to accept (or "listen" for) these events, and execute code in response to process (or "handle") them. Event-handlers are usually connected (or "attached") to various HTML elements (such as <button>
, <div>
, <span>
, etc.) using EventTarget.addEventListener()
, and this generally replaces using the old HTML event handler attributes. Further, when properly added, such handlers can also be disconnected if needed using removeEventListener()
.
Note: One element can have several such handlers, even for the exact same eventâparticularly if separate, independent code modules attach them, each for its own independent purposes. (For example, a webpage with an advertising-module and statistics-module both monitoring video-watching.)
When there are many nested elements, each with its own handler(s), event processing can become very complicatedâespecially where a parent element receives the very same event as its child elements because "spatially" they overlap so the event technically occurs in both, and the processing order of such events depends on the Event bubbling settings of each handler triggered.
Interfaces based on Event ConstructorEvent()
Creates an Event
object, returning it to the caller.
Event.bubbles
Read only
A boolean value indicating whether or not the event bubbles up through the DOM.
Event.cancelable
Read only
A boolean value indicating whether the event is cancelable.
Event.composed
Read only
A boolean indicating whether or not the event can bubble across the boundary between the shadow DOM and the regular DOM.
Event.currentTarget
Read only
A reference to the currently registered target for the event. This is the object to which the event is currently slated to be sent. It's possible this has been changed along the way through retargeting.
Event.defaultPrevented
Read only
Indicates whether or not the call to event.preventDefault()
canceled the event.
Event.eventPhase
Read only
Indicates which phase of the event flow is being processed. It is one of the following numbers: NONE
, CAPTURING_PHASE
, AT_TARGET
, BUBBLING_PHASE
.
Event.isTrusted
Read only
Indicates whether or not the event was initiated by the browser (after a user click, for instance) or by a script (using an event creation method, for example).
Event.srcElement
Read only Deprecated
An alias for the Event.target
property. Use Event.target
instead.
Event.target
Read only
A reference to the object to which the event was originally dispatched.
Event.timeStamp
Read only
The time at which the event was created (in milliseconds). By specification, this value is time since epochâbut in reality, browsers' definitions vary. In addition, work is underway to change this to be a DOMHighResTimeStamp
instead.
Event.type
Read only
The name identifying the type of the event.
Event.cancelBubble
Deprecated
A historical alias to Event.stopPropagation()
that should be used instead. Setting its value to true
before returning from an event handler prevents propagation of the event.
Event.explicitOriginalTarget
Non-standard Read only
The explicit original target of the event.
Event.originalTarget
Non-standard Read only
The original target of the event, before any retargetings.
Event.returnValue
Deprecated
A historical property still supported in order to ensure existing sites continue to work. Use Event.preventDefault()
and Event.defaultPrevented
instead.
Event.scoped
Read only Deprecated
A boolean value indicating whether the given event will bubble across through the shadow root into the standard DOM. Use composed
instead.
Event.composedPath()
Returns the event's path (an array of objects on which listeners will be invoked). This does not include nodes in shadow trees if the shadow root was created with its ShadowRoot.mode
closed.
Event.preventDefault()
Cancels the event (if it is cancelable).
Event.stopImmediatePropagation()
For this particular event, prevent all other listeners from being called. This includes listeners attached to the same element as well as those attached to elements that will be traversed later (during the capture phase, for instance).
Event.stopPropagation()
Stops the propagation of events further along in the DOM.
Event.initEvent()
Deprecated
Initializes the value of an Event created. If the event has already been dispatched, this method does nothing. Use the constructor (Event()
instead).
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