Method once

packages/firebase-database/common.ts:28–28

(eventType: EventType, successCallback?: undefined | ((a: IDataSnapshot, b: string | null) => any), failureCallbackContext?: (a: Error) => void | Record<string, any> | null)

	off(eventType?: EventType, callback?: undefined | ((a: IDataSnapshot, b: string | null) => void), context?: Record<string, any>): void;
	on(eventType: EventType, callback: (data: IDataSnapshot, previousChildKey: string | null) => void, cancelCallbackOrContext?: (a: Error) => void | Record<string, any> | null, context?: Record<string, any> | null): (a: IDataSnapshot | null, b: string | null) => void;
	once(eventType: EventType, successCallback?: undefined | ((a: IDataSnapshot, b: string | null) => any), failureCallbackContext?: (a: Error) => void | Record<string, any> | null): Promise<IDataSnapshot>;
	orderByChild(path: string): IQuery;
	orderByKey(): IQuery;
	orderByPriority(): IQuery;