export interface Event {
    type: string;
    target?: any;
}
type Listener = (evt: Event) => any;
type ListenerRegistry = {
    [type: string]: Listener[];
};
/**
 * An event source can emit events and register event listeners
 */
export default class EventSource {
    _listeners: ListenerRegistry;
    _onceListeners: ListenerRegistry;
    /**
     * Adds a listener to a event type.
     */
    on(type: string, listener: Listener): void;
    /**
     * Adds a listener that will be called only once to a event type.
     */
    once(type: string, listener: Listener): void;
    /**
     * Removes a previously registered event listener.
     */
    off(type: string, listener: Listener): void;
    emit(eventOrType: string | Event): void;
    /**
     * Returns true if we have a listener for the event type.
     */
    private _listens;
}
export {};