nsIDOMEvent
nseventptr getinternalnsevent(); violates the xpcom interface guidelines boolean getpreventdefault(); deprecated since gecko 16.0 void initevent(in domstring eventtypearg, in boolean canbubblearg, in boolean cancelablearg); boolean isdispatchstopped(); violates the xpcom interface guidelines void preventbubble(); obsolete since gecko 24 void preventcapture(); obsolete since gecko 24 void preventdefault(); void serialize(in ipcmessageptr amsg, in boolean aserializeinterfacetype); violates the xpcom interface guidelines void settarget(in nsidomeventtarget atarget); native code only!
... return value preventbubble() note: use stoppropagation() instead.
... void preventbubble(); parameters none.

Chapter 5: Let's build a Firefox extension - Archive of obsolete content
listing 21: content for clear method clear: function(event) { event.preventbubble(); var fileenum = this._dir.directoryentries; while (fileenum.hasmoreelements()) { var file = fileenum.getnext().queryinterface(components.interfaces.nsifile); file.remove(false); // debug dump("sessionstore> clear: " + file.leafname + "\n"); } }, _readfile method reads the nslfile object passed as a parameter, and returns its contents as a text string.

CustomEvent - Web APIs
(returns the value of event.defaultprevented.) event.preventbubble() obsolete since gecko 24 obsolete; use event.stoppropagation instead.

Event - Web APIs
event.preventbubble() prevents the event from bubbling.