Query regarding canTrigger() method of EventTarget Interface

Hi,

I have a query on the canTrigger() method introduced in DOM Events level
3 Specification. The specification says that:

 

This method allows the DOM application to know if an event listener,
attached to this

EventTarget or one of its ancestors, will be triggered by the specified
event type during

the dispatch of the event to this event target or one of its
descendants.

Parameters

type of type DOMString

The event type for which the EventListener is registered.

Return Value

boolean true if an event listener will be triggered on the event target
with the

specified event type, false otherwise.

 

Does it mean that we need to check if there are any event listeners of
the event type passed as parameter registered on the eventTarget or its
ancestors? 

If there are any listeners of the particular event type registered,
canTrigger() will return true else false. I mean what is the basis of
determining that an event will be triggered? Secondly, are we talking
about the capture phase when we say dispatch of the event to the event
target or one of its descendants.

 

Regards,

Sarika.