dispatchEvent

dispatchEvent is a method defined on the EventTarget interface in the DOM that dispatches an Event object to the target, triggering any listeners registered for the event type. It can be used with standard events or with custom events created via CustomEvent.

To use dispatchEvent, create an Event or CustomEvent object and pass it to the target’s dispatchEvent method. The method returns a boolean: it returns false if preventDefault has been called on the event, and true if the event’s default action was not prevented. This return value allows code to react to whether any listener canceled the event.

Events may participate in the DOM’s propagation model. If the event’s bubbles option is true, the event travels up through the ancestor chain during the bubble phase, invoking listeners along the way. Listeners registered with capture: true will run during the capture phase, before the target’s own listeners. The composed option determines whether the event can cross shadow DOM boundaries. The event’s phase, target, and currentTarget properties describe where the event is in its delivery.

Listeners are registered with addEventListener(type, listener, options). A listener receives the event object and may call preventDefault, stopPropagation, or stopImmediatePropagation to alter behavior or propagation. If there are no listeners for a given type, dispatchEvent simply returns true.

Common usage includes creating custom events with data stored in the detail property of a CustomEvent and then dispatching them on a chosen element. In environments without a DOM EventTarget, dispatchEvent is not available; equivalents exist in other event systems, such as EventEmitter in Node.js.