Event class Null safety
The Event interface represents an event which takes place in the DOM.
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 interface. 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
<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
Note: One element can have several such handlers, even for the
exact same event—particularly 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
complicated—especially 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 and capture settings
of each handler triggered.
- bubbles → bool
A boolean indicating whether or not the event bubbles up through
- cancelable → bool
A boolean indicating whether the event is cancelable.
- cancelBubble ↔ bool
A historical alias to Event.stopPropagation(). Setting its
truebefore returning from an event handler prevents propagation of the event.read / write
- composed → bool
A boolean indicating whether or not the event can bubble across
the boundary between the shadow DOM and the regular DOM.
- currentTarget → EventTarget?
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
- defaultPrevented → bool
Indicates whether or not the call to
event.preventDefault()canceled the event.read-only
- eventPhase → int
Indicates which phase of the event flow is being processed.
- hashCode → int
The hash code for this object. [...]
- isTrusted → bool
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, like Event.initEvent).
- returnValue ↔ dynamic
A historical property introduced by Internet Explorer and
eventually adopted into the DOM specification in order to ensure
existing sites continue to work. Ideally, you should try to use
Event.preventDefault() and Event.defaultPrevented instead,
but you can use if you choose to do so.
covariant, read / write
- runtimeType → Type
A representation of the runtime type of the object.
- srcElement → EventTarget?
A non-standard alias (from old versions of Microsoft Internet
Explorer) for Event.target. Some other browsers are starting to
support it for web compatibility purposes.
- target → EventTarget?
A reference to the target to which the event was originally
- timeStamp → double
The time at which the event was created (in milliseconds). By
specification, this value is time since epoch—but in reality,
browsers' definitions vary. In addition, work is underway to
change this to be a
- type → String
The name of the event. Case-insensitive.
) → Iterable< EventTarget>
- Returns the event’s path (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. var composed = Event.composedPath();
String type, [bool? bubbles = false, bool? cancelable = false]) → Object
Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
) → Object
- Cancels the event (if it is cancelable). event.preventDefault();
) → Object
- 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.stopImmediatePropagation();
) → Object
- Stops the propagation of events further along in the DOM. event.stopPropagation();
) → String
A string representation of this object. [...]