Event.cancelable
The cancelable
read-only property of the Event
interface indicates whether the event
can be canceled, and therefore prevented as if the event never happened. If the
event is not cancelable, then its cancelable
property will be
false
and the event listener cannot stop the event from occurring.
Event listeners that handle multiple kinds of events may want to check
cancelable
before invoking their preventDefault()
methods.
Most browser-native events that can be canceled are the ones that result from the user
interacting with the page. Canceling the click
,
scroll
, or
beforeunload
events would prevent the user
from clicking on something, scrolling the page, or navigating away from the page,
respectively.
Custom events created by other JavaScript code control if they can be canceled when they are created.
Syntax
bool = event.cancelable;
Value
The result is a Boolean
, which is true
if the event can be
canceled.
Example
For example, browser vendors are proposing that the wheel
event can only be canceled the first time
the listener is called — any following wheel
events cannot be
canceled.
function preventScrollWheel(event) {
if (typeof event.cancelable !== 'boolean' || event.cancelable) {
// The event can be canceled, so we do so.
event.preventDefault();
} else {
// The event cannot be canceled, so it is not safe
// to call preventDefault() on it.
console.warn(`The following event couldn't be canceled:`);
console.dir(event);
}
}
document.addEventListener('wheel', preventScrollWheel);
Notes
Whether an event can be canceled or not is something that's determined when that event is initialized.
To cancel an event, call the preventDefault()
method on the event. This keeps the implementation from executing the default action
that is associated with the event.
Specifications
Specification | Status | Comment |
---|---|---|
DOM The definition of 'Event.cancelable' in that specification. |
Living Standard | |
Document Object Model (DOM) Level 2 Events Specification The definition of 'Event.cancelable' in that specification. |
Obsolete | Initial definition. |
Browser compatibility
BCD tables only load in the browser