src/EventEmitter.js
/**
         * Registers an event handler to fire on any occurrence of an event
         * @param event
         * @param listener
         */
Registers an event handler to fire on any occurrence of an event
@param event
@param listener
Registers an event handler to fire on any occurrence of an event @param event @param listener
on(event, listener) {
            if (!this._events[event]) {
                this._events[event] = [];
            }
            this._events[event].push(listener);
        }
on ( event , listener ) { if ( ! this . _events [ event ] ) { this . _events [ event ] = [ ] ; } this . _events [ event ] . push ( listener ) ; }
Registers an event handler to fire on any occurrence of an event
 @param event
 @param listener
Registers an event handler to fire on any occurrence of an event @param event @param listener