TaskPriorityChangeEvent

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Note: This feature is available in Web Workers.

The TaskPriorityChangeEvent is the interface for the prioritychange event.

Event TaskPriorityChangeEvent

Constructor

TaskPriorityChangeEvent()

Creates a new TaskPriorityChangeEvent object, setting an event name and previous priority.

Instance properties

This interface also inherits the properties of its parent, Event.

TaskPriorityChangeEvent.previousPriority Read only

Returns the priority of the corresponding TaskSignal before this prioritychange event.

Instance methods

This interface has no methods of its own, but inherits the methods of its parent, Event.

Examples

An object of this type is returned in the handler for a prioritychange event. The code below shows a handler in which the newPriority and previousPriority are logged.

js
// Listen for 'prioritychange' events on the controller's signal.
controller.signal.addEventListener("prioritychange", (event) => {
  const previousPriority = event.previousPriority;
  const newPriority = event.target.priority;
  console.log(`Priority changed from ${previousPriority} to ${newPriority}.`);
});

A more complete live example can be found in prioritychange event > Examples.

Specifications

Specification
Prioritized Task Scheduling
# sec-task-priority-change-event

Browser compatibility

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
TaskPriorityChangeEvent
Chrome – Full support
Chrome 94 (Release date: 2021-09-21)
footnote Full support
Edge – Full support
Edge 94 (Release date: 2021-09-24)
footnote Full support
Firefox – Full support
Firefox 142 (Release date: 2025-08-19)
footnote Full support
Opera – Full support
Opera 80 (Release date: 2021-10-05)
footnote Full support
Safari – No support
Safari
footnote No support
Chrome Android – Full support
Chrome Android 94 (Release date: 2021-09-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 142 (Release date: 2025-08-19)
footnote Full support
Opera Android – Full support
Opera Android 66 (Release date: 2021-12-15)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote No support
Samsung Internet – Full support
Samsung Internet 17 (Release date: 2022-05-04)
footnote Full support
WebView Android – Full support
WebView Android 94 (Release date: 2021-09-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
TaskPriorityChangeEvent() constructor
Chrome – Full support
Chrome 94 (Release date: 2021-09-21)
footnote Full support
Edge – Full support
Edge 94 (Release date: 2021-09-24)
footnote Full support
Firefox – Full support
Firefox 142 (Release date: 2025-08-19)
footnote Full support
Opera – Full support
Opera 80 (Release date: 2021-10-05)
footnote Full support
Safari – No support
Safari
footnote No support
Chrome Android – Full support
Chrome Android 94 (Release date: 2021-09-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 142 (Release date: 2025-08-19)
footnote Full support
Opera Android – Full support
Opera Android 66 (Release date: 2021-12-15)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote No support
Samsung Internet – Full support
Samsung Internet 17 (Release date: 2022-05-04)
footnote Full support
WebView Android – Full support
WebView Android 94 (Release date: 2021-09-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
previousPriority
Chrome – Full support
Chrome 94 (Release date: 2021-09-21)
footnote Full support
Edge – Full support
Edge 94 (Release date: 2021-09-24)
footnote Full support
Firefox – Full support
Firefox 142 (Release date: 2025-08-19)
footnote Full support
Opera – Full support
Opera 80 (Release date: 2021-10-05)
footnote Full support
Safari – No support
Safari
footnote No support
Chrome Android – Full support
Chrome Android 94 (Release date: 2021-09-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 142 (Release date: 2025-08-19)
footnote Full support
Opera Android – Full support
Opera Android 66 (Release date: 2021-12-15)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote No support
Samsung Internet – Full support
Samsung Internet 17 (Release date: 2022-05-04)
footnote Full support
WebView Android – Full support
WebView Android 94 (Release date: 2021-09-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support

See also