export default class EventEmitter { _events : { [ key ] : Array < ( ... args : any [ ] ) => void > ; } ; _maxListeners : number = 10 ; /**
     * Instantiate the class.
     */ constructor ( ) { this . _events = { } ; } return { Number } getMaxListeners ( ) { return this . _maxListeners ; } param { Number } n setMaxListeners ( n ) { return this . _maxListeners = n ; } param { String } event param { ( ... args : any [ ] ) => void } listener on ( event , listener ) { if ( this . _events [ event ] == null ) { this . _events [ event ] = [ ] ; } const n = this . _events [ event ] . push ( listener ) ; if ( n > this . _maxListeners ) { console . warn ( `Possible EventEmitter memory leak detected. ${ n } "${ event }" listener(s) added. Use emitter.setMaxListeners() to increase limit.` ) ; } } param { String } event param { ( ... args : any [ ] ) => void } listener once ( event , listener ) { const once = ( ... args ) => { listener ( ... args ) ; this . off ( event , once ) ; } ; this . on ( event , once ) ; } param { String } event param { ( ... args : any [ ] ) => void } listener off ( event , listener ) { const listeners = this . _events [ event ] ; if ( listeners && listeners . length ) { for ( let i = listeners . length - 1 ; i >= 0 ; -- i ) { if ( listeners [ i ] === listener ) { listeners . splice ( i , 1 ) ; break ; } } } } param { String } event return { Boolean } emit ( event , ... args ) { const listeners = this . _events [ event ] ; const listenersExist = ! ! ( listeners && listeners . length ) ; if ( listenersExist ) { for ( let i = 0 ; i < listeners . length ; ++ i ) { listeners [ i ] ( ... args ) ; } } if ( event != 'all' ) { this . emit ( 'all' , ... args ) ; } return listenersExist ; } }