declare type AnyFn = (...params: any[]) => void;
declare type NameBy<O> = (keyof O & string) | string | number;
declare type ListenerBy<O, K> = K extends keyof O ? O[K] : AnyFn;
export declare class EventEmitter<O extends {
    [k in keyof O]: AnyFn;
} = any> {
    private _o;
    on<K extends NameBy<O>>(name: K, listener: ListenerBy<O, K>): () => void;
    off<K extends NameBy<O>>(name: K, listener?: ListenerBy<O, K>): void;
    once<K extends NameBy<O>>(name: K, listener: ListenerBy<O, K>): () => void;
    emit<K extends NameBy<O>>(name: K, ...params: Parameters<ListenerBy<O, K>>): void;
    has<K extends NameBy<O>>(name: K, listener?: ListenerBy<O, K>): boolean;
}
export default EventEmitter;