nl_tokens: https : // dom . spec . whatwg . org / #interface - eventtarget
pl_tokens: function createEventListener ( type , callback , options ) { function eventListener ( e ) { if ( eventListener . once ) { e . currentTarget . removeEventListener ( e . type , callback , eventListener ) ; eventListener . removed = true ; } if ( eventListener . passive ) { e . preventDefault = createEventListener . preventDefault ; } if ( typeof eventListener . callback === 'function' ) { /* jshint validthis: true */ eventListener . callback . call ( this , e ) ; } else if ( eventListener . callback ) { eventListener . callback . handleEvent ( e ) ; } if ( eventListener . passive ) { delete e . preventDefault ; } } eventListener . <mask> = type ; eventListener . callback = callback ; eventListener . capture = ! ! options . capture ; eventListener . passive = ! ! options . passive ; eventListener . once = ! ! options . once ; // currently pointless but specs say to use it, so ... eventListener . removed = false ; return eventListener ; }