@firebase/database/dist/public.d.ts

This is the Firebase Realtime Database component of the Firebase JS SDK.

/**
 * Firebase Realtime Database
 *
 * @packageDocumentation
 */
import { FirebaseApp } from '@firebase/app';
import { EmulatorMockTokenOptions } from '@firebase/util';

/**
 * Gets a `Reference` for the location at the specified relative path.
 *
 * The relative path can either be a simple child name (for example, "ada") or
 * a deeper slash-separated path (for example, "ada/name/first").
 *
 * @param parent - The parent location.
 * @param path - A relative path from this location to the desired child
 *   location.
 * @returns The specified child location.
 */
export declare function child(parent: DatabaseReference, path: string): DatabaseReference;
/**
 * Modify the provided instance to communicate with the Realtime Database
 * emulator.
 *
 * <p>Note: This method must be called before performing any other operation.
 *
 * @param db - The instance to modify.
 * @param host - The emulator host (ex: localhost)
 * @param port - The emulator port (ex: 8080)
 * @param options.mockUserToken - the mock auth token to use for unit testing Security Rules
 */
export declare function connectDatabaseEmulator(db: Database, host: string, port: number, options?: {
    mockUserToken?: EmulatorMockTokenOptions | string;
}): void;
/**
 * Class representing a Firebase Realtime Database.
 */
export declare class Database {
    /** The {@link @firebase/app#FirebaseApp} associated with this Realtime Database instance. */
    readonly app: FirebaseApp;
    /** Represents a `Database` instance. */
    readonly 'type' = "database";
    private constructor();
}
/**
 * A `DatabaseReference` represents a specific location in your Database and can be used
 * for reading or writing data to that Database location.
 *
 * You can reference the root or child location in your Database by calling
 * `ref()` or `ref("child/path")`.
 *
 * Writing is done with the `set()` method and reading can be done with the
 * `on*()` method. See {@link
 * https://firebase.google.com/docs/database/web/read-and-write}
 */
export declare interface DatabaseReference extends Query {
    /**
     * The last part of the `DatabaseReference`'s path.
     *
     * For example, `"ada"` is the key for
     * `https://<DATABASE_NAME>.firebaseio.com/users/ada`.
     *
     * The key of a root `DatabaseReference` is `null`.
     */
    readonly key: string | null;
    /**
     * The parent location of a `DatabaseReference`.
     *
     * The parent of a root `DatabaseReference` is `null`.
     */
    readonly parent: DatabaseReference | null;
    /** The root `DatabaseReference` of the Database. */
    readonly root: DatabaseReference;
}
/**
 * A `DataSnapshot` contains data from a Database location.
 *
 * Any time you read data from the Database, you receive the data as a
 * `DataSnapshot`. A `DataSnapshot` is passed to the event callbacks you attach
 * with `on()` or `once()`. You can extract the contents of the snapshot as a
 * JavaScript object by calling the `val()` method. Alternatively, you can
 * traverse into the snapshot by calling `child()` to return child snapshots
 * (which you could then call `val()` on).
 *
 * A `DataSnapshot` is an efficiently generated, immutable copy of the data at
 * a Database location. It cannot be modified and will never change (to modify
 * data, you always call the `set()` method on a `Reference` directly).
 */
export declare class DataSnapshot {
    /**
     * The location of this DataSnapshot.
     */
    readonly ref: DatabaseReference;
    private constructor();
    /**
     * Gets the priority value of the data in this `DataSnapshot`.
     *
     * Applications need not use priority but can order collections by
     * ordinary properties (see
     * {@link https://firebase.google.com/docs/database/web/lists-of-data#sorting_and_filtering_data |Sorting and filtering data}
     * ).
     */
    get priority(): string | number | null;
    /**
     * The key (last part of the path) of the location of this `DataSnapshot`.
     *
     * The last token in a Database location is considered its key. For example,
     * "ada" is the key for the /users/ada/ node. Accessing the key on any
     * `DataSnapshot` will return the key for the location that generated it.
     * However, accessing the key on the root URL of a Database will return
     * `null`.
     */
    get key(): string | null;
    /** Returns the number of child properties of this `DataSnapshot`. */
    get size(): number;
    /**
     * Gets another `DataSnapshot` for the location at the specified relative path.
     *
     * Passing a relative path to the `child()` method of a DataSnapshot returns
     * another `DataSnapshot` for the location at the specified relative path. The
     * relative path can either be a simple child name (for example, "ada") or a
     * deeper, slash-separated path (for example, "ada/name/first"). If the child
     * location has no data, an empty `DataSnapshot` (that is, a `DataSnapshot`
     * whose value is `null`) is returned.
     *
     * @param path - A relative path to the location of child data.
     */
    child(path: string): DataSnapshot;
    /**
     * Returns true if this `DataSnapshot` contains any data. It is slightly more
     * efficient than using `snapshot.val() !== null`.
     */
    exists(): boolean;
    /**
     * Exports the entire contents of the DataSnapshot as a JavaScript object.
     *
     * The `exportVal()` method is similar to `val()`, except priority information
     * is included (if available), making it suitable for backing up your data.
     *
     * @returns The DataSnapshot's contents as a JavaScript value (Object,
     *   Array, string, number, boolean, or `null`).
     */
    exportVal(): any;
    /**
     * Enumerates the top-level children in the `IteratedDataSnapshot`.
     *
     * Because of the way JavaScript objects work, the ordering of data in the
     * JavaScript object returned by `val()` is not guaranteed to match the
     * ordering on the server nor the ordering of `onChildAdded()` events. That is
     * where `forEach()` comes in handy. It guarantees the children of a
     * `DataSnapshot` will be iterated in their query order.
     *
     * If no explicit `orderBy*()` method is used, results are returned
     * ordered by key (unless priorities are used, in which case, results are
     * returned by priority).
     *
     * @param action - A function that will be called for each child DataSnapshot.
     * The callback can return true to cancel further enumeration.
     * @returns true if enumeration was canceled due to your callback returning
     * true.
     */
    forEach(action: (child: IteratedDataSnapshot) => boolean | void): boolean;
    /**
     * Returns true if the specified child path has (non-null) data.
     *
     * @param path - A relative path to the location of a potential child.
     * @returns `true` if data exists at the specified child path; else
     *  `false`.
     */
    hasChild(path: string): boolean;
    /**
     * Returns whether or not the `DataSnapshot` has any non-`null` child
     * properties.
     *
     * You can use `hasChildren()` to determine if a `DataSnapshot` has any
     * children. If it does, you can enumerate them using `forEach()`. If it
     * doesn't, then either this snapshot contains a primitive value (which can be
     * retrieved with `val()`) or it is empty (in which case, `val()` will return
     * `null`).
     *
     * @returns true if this snapshot has any children; else false.
     */
    hasChildren(): boolean;
    /**
     * Returns a JSON-serializable representation of this object.
     */
    toJSON(): object | null;
    /**
     * Extracts a JavaScript value from a `DataSnapshot`.
     *
     * Depending on the data in a `DataSnapshot`, the `val()` method may return a
     * scalar type (string, number, or boolean), an array, or an object. It may
     * also return null, indicating that the `DataSnapshot` is empty (contains no
     * data).
     *
     * @returns The DataSnapshot's contents as a JavaScript value (Object,
     *   Array, string, number, boolean, or `null`).
     */
    val(): any;
}
export { EmulatorMockTokenOptions };
/**
 * Logs debugging information to the console.
 *
 * @param enabled - Enables logging if `true`, disables logging if `false`.
 * @param persistent - Remembers the logging state between page refreshes if
 * `true`.
 */
export declare function enableLogging(enabled: boolean, persistent?: boolean): any;
/**
 * Logs debugging information to the console.
 *
 * @param logger - A custom logger function to control how things get logged.
 */
export declare function enableLogging(logger: (message: string) => unknown): any;
/**
 * Creates a `QueryConstraint` with the specified ending point.
 *
 * Using `startAt()`, `startAfter()`, `endBefore()`, `endAt()` and `equalTo()`
 * allows you to choose arbitrary starting and ending points for your queries.
 *
 * The ending point is inclusive, so children with exactly the specified value
 * will be included in the query. The optional key argument can be used to
 * further limit the range of the query. If it is specified, then children that
 * have exactly the specified value must also have a key name less than or equal
 * to the specified key.
 *
 * You can read more about `endAt()` in
 * {@link https://firebase.google.com/docs/database/web/lists-of-data#filtering_data | Filtering data}.
 *
 * @param value - The value to end at. The argument type depends on which
 * `orderBy*()` function was used in this query. Specify a value that matches
 * the `orderBy*()` type. When used in combination with `orderByKey()`, the
 * value must be a string.
 * @param key - The child key to end at, among the children with the previously
 * specified priority. This argument is only allowed if ordering by child,
 * value, or priority.
 */
export declare function endAt(value: number | string | boolean | null, key?: string): QueryConstraint;
/**
 * Creates a `QueryConstraint` with the specified ending point (exclusive).
 *
 * Using `startAt()`, `startAfter()`, `endBefore()`, `endAt()` and `equalTo()`
 * allows you to choose arbitrary starting and ending points for your queries.
 *
 * The ending point is exclusive. If only a value is provided, children
 * with a value less than the specified value will be included in the query.
 * If a key is specified, then children must have a value less than or equal
 * to the specified value and a key name less than the specified key.
 *
 * @param value - The value to end before. The argument type depends on which
 * `orderBy*()` function was used in this query. Specify a value that matches
 * the `orderBy*()` type. When used in combination with `orderByKey()`, the
 * value must be a string.
 * @param key - The child key to end before, among the children with the
 * previously specified priority. This argument is only allowed if ordering by
 * child, value, or priority.
 */
export declare function endBefore(value: number | string | boolean | null, key?: string): QueryConstraint;
/**
 * Creates a `QueryConstraint` that includes children that match the specified
 * value.
 *
 * Using `startAt()`, `startAfter()`, `endBefore()`, `endAt()` and `equalTo()`
 * allows you to choose arbitrary starting and ending points for your queries.
 *
 * The optional key argument can be used to further limit the range of the
 * query. If it is specified, then children that have exactly the specified
 * value must also have exactly the specified key as their key name. This can be
 * used to filter result sets with many matches for the same value.
 *
 * You can read more about `equalTo()` in
 * {@link https://firebase.google.com/docs/database/web/lists-of-data#filtering_data | Filtering data}.
 *
 * @param value - The value to match for. The argument type depends on which
 * `orderBy*()` function was used in this query. Specify a value that matches
 * the `orderBy*()` type. When used in combination with `orderByKey()`, the
 * value must be a string.
 * @param key - The child key to start at, among the children with the
 * previously specified priority. This argument is only allowed if ordering by
 * child, value, or priority.
 */
export declare function equalTo(value: number | string | boolean | null, key?: string): QueryConstraint;
/**
 * One of the following strings: "value", "child_added", "child_changed",
 * "child_removed", or "child_moved."
 */
export declare type EventType = 'value' | 'child_added' | 'child_changed' | 'child_moved' | 'child_removed';
/* Excluded from this release type: _FirebaseService */
/**
 * Force the use of longPolling instead of websockets. This will be ignored if websocket protocol is used in databaseURL.
 */
export declare function forceLongPolling(): void;
/**
 * Force the use of websockets instead of longPolling.
 */
export declare function forceWebSockets(): void;
/**
 * Gets the most up-to-date result for this query.
 *
 * @param query - The query to run.
 * @returns A `Promise` which resolves to the resulting DataSnapshot if a value is
 * available, or rejects if the client is unable to return a value (e.g., if the
 * server is unreachable and there is nothing cached).
 */
export declare function get(query: Query): Promise<DataSnapshot>;
/**
 * Returns the instance of the Realtime Database SDK that is associated with the provided
 * {@link @firebase/app#FirebaseApp}. Initializes a new instance with default settings if
 * no instance exists or if the existing instance uses a custom database URL.
 *
 * @param app - The {@link @firebase/app#FirebaseApp} instance that the returned Realtime
 * Database instance is associated with.
 * @param url - The URL of the Realtime Database instance to connect to. If not
 * provided, the SDK connects to the default instance of the Firebase App.
 * @returns The `Database` instance of the provided app.
 */
export declare function getDatabase(app?: FirebaseApp, url?: string): Database;
/**
 * Disconnects from the server (all Database operations will be completed
 * offline).
 *
 * The client automatically maintains a persistent connection to the Database
 * server, which will remain active indefinitely and reconnect when
 * disconnected. However, the `goOffline()` and `goOnline()` methods may be used
 * to control the client connection in cases where a persistent connection is
 * undesirable.
 *
 * While offline, the client will no longer receive data updates from the
 * Database. However, all Database operations performed locally will continue to
 * immediately fire events, allowing your application to continue behaving
 * normally. Additionally, each operation performed locally will automatically
 * be queued and retried upon reconnection to the Database server.
 *
 * To reconnect to the Database and begin receiving remote events, see
 * `goOnline()`.
 *
 * @param db - The instance to disconnect.
 */
export declare function goOffline(db: Database): void;
/**
 * Reconnects to the server and synchronizes the offline Database state
 * with the server state.
 *
 * This method should be used after disabling the active connection with
 * `goOffline()`. Once reconnected, the client will transmit the proper data
 * and fire the appropriate events so that your client "catches up"
 * automatically.
 *
 * @param db - The instance to reconnect.
 */
export declare function goOnline(db: Database): void;
/**
 * Returns a placeholder value that can be used to atomically increment the
 * current database value by the provided delta.
 *
 * @param delta - the amount to modify the current value atomically.
 * @returns A placeholder value for modifying data atomically server-side.
 */
export declare function increment(delta: number): object;
/* Excluded from this release type: _initStandalone */
/**
 * Represents a child snapshot of a `Reference` that is being iterated over. The key will never be undefined.
 */
export declare interface IteratedDataSnapshot extends DataSnapshot {
    key: string;
}
/**
 * Creates a new `QueryConstraint` that if limited to the first specific number
 * of children.
 *
 * The `limitToFirst()` method is used to set a maximum number of children to be
 * synced for a given callback. If we set a limit of 100, we will initially only
 * receive up to 100 `child_added` events. If we have fewer than 100 messages
 * stored in our Database, a `child_added` event will fire for each message.
 * However, if we have over 100 messages, we will only receive a `child_added`
 * event for the first 100 ordered messages. As items change, we will receive
 * `child_removed` events for each item that drops out of the active list so
 * that the total number stays at 100.
 *
 * You can read more about `limitToFirst()` in
 * {@link https://firebase.google.com/docs/database/web/lists-of-data#filtering_data | Filtering data}.
 *
 * @param limit - The maximum number of nodes to include in this query.
 */
export declare function limitToFirst(limit: number): QueryConstraint;
/**
 * Creates a new `QueryConstraint` that is limited to return only the last
 * specified number of children.
 *
 * The `limitToLast()` method is used to set a maximum number of children to be
 * synced for a given callback. If we set a limit of 100, we will initially only
 * receive up to 100 `child_added` events. If we have fewer than 100 messages
 * stored in our Database, a `child_added` event will fire for each message.
 * However, if we have over 100 messages, we will only receive a `child_added`
 * event for the last 100 ordered messages. As items change, we will receive
 * `child_removed` events for each item that drops out of the active list so
 * that the total number stays at 100.
 *
 * You can read more about `limitToLast()` in
 * {@link https://firebase.google.com/docs/database/web/lists-of-data#filtering_data | Filtering data}.
 *
 * @param limit - The maximum number of nodes to include in this query.
 */
export declare function limitToLast(limit: number): QueryConstraint;
/** An options objects that can be used to customize a listener. */
export declare interface ListenOptions {
    /** Whether to remove the listener after its first invocation. */
    readonly onlyOnce?: boolean;
}
/**
 * Detaches a callback previously attached with the corresponding `on*()` (`onValue`, `onChildAdded`) listener.
 * Note: This is not the recommended way to remove a listener. Instead, please use the returned callback function from
 * the respective `on*` callbacks.
 *
 * Detach a callback previously attached with `on*()`. Calling `off()` on a parent listener
 * will not automatically remove listeners registered on child nodes, `off()`
 * must also be called on any child listeners to remove the callback.
 *
 * If a callback is not specified, all callbacks for the specified eventType
 * will be removed. Similarly, if no eventType is specified, all callbacks
 * for the `Reference` will be removed.
 *
 * Individual listeners can also be removed by invoking their unsubscribe
 * callbacks.
 *
 * @param query - The query that the listener was registered with.
 * @param eventType - One of the following strings: "value", "child_added",
 * "child_changed", "child_removed", or "child_moved." If omitted, all callbacks
 * for the `Reference` will be removed.
 * @param callback - The callback function that was passed to `on()` or
 * `undefined` to remove all callbacks.
 */
export declare function off(query: Query, eventType?: EventType, callback?: (snapshot: DataSnapshot, previousChildName?: string | null) => unknown): void;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildAdded` event will be triggered once for each initial child at this
 * location, and it will be triggered again every time a new child is added. The
 * `DataSnapshot` passed into the callback will reflect the data for the
 * relevant child. For ordering purposes, it is passed a second argument which
 * is a string containing the key of the previous sibling child by sort order,
 * or `null` if it is the first child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildAdded(query: Query, callback: (snapshot: DataSnapshot, previousChildName?: string | null) => unknown, cancelCallback?: (error: Error) => unknown): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildAdded` event will be triggered once for each initial child at this
 * location, and it will be triggered again every time a new child is added. The
 * `DataSnapshot` passed into the callback will reflect the data for the
 * relevant child. For ordering purposes, it is passed a second argument which
 * is a string containing the key of the previous sibling child by sort order,
 * or `null` if it is the first child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildAdded(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildAdded` event will be triggered once for each initial child at this
 * location, and it will be triggered again every time a new child is added. The
 * `DataSnapshot` passed into the callback will reflect the data for the
 * relevant child. For ordering purposes, it is passed a second argument which
 * is a string containing the key of the previous sibling child by sort order,
 * or `null` if it is the first child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildAdded(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, cancelCallback: (error: Error) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildChanged` event will be triggered when the data stored in a child
 * (or any of its descendants) changes. Note that a single `child_changed` event
 * may represent multiple changes to the child. The `DataSnapshot` passed to the
 * callback will contain the new child contents. For ordering purposes, the
 * callback is also passed a second argument which is a string containing the
 * key of the previous sibling child by sort order, or `null` if it is the first
 * child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildChanged(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, cancelCallback?: (error: Error) => unknown): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildChanged` event will be triggered when the data stored in a child
 * (or any of its descendants) changes. Note that a single `child_changed` event
 * may represent multiple changes to the child. The `DataSnapshot` passed to the
 * callback will contain the new child contents. For ordering purposes, the
 * callback is also passed a second argument which is a string containing the
 * key of the previous sibling child by sort order, or `null` if it is the first
 * child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildChanged(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildChanged` event will be triggered when the data stored in a child
 * (or any of its descendants) changes. Note that a single `child_changed` event
 * may represent multiple changes to the child. The `DataSnapshot` passed to the
 * callback will contain the new child contents. For ordering purposes, the
 * callback is also passed a second argument which is a string containing the
 * key of the previous sibling child by sort order, or `null` if it is the first
 * child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildChanged(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, cancelCallback: (error: Error) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildMoved` event will be triggered when a child's sort order changes
 * such that its position relative to its siblings changes. The `DataSnapshot`
 * passed to the callback will be for the data of the child that has moved. It
 * is also passed a second argument which is a string containing the key of the
 * previous sibling child by sort order, or `null` if it is the first child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildMoved(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, cancelCallback?: (error: Error) => unknown): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildMoved` event will be triggered when a child's sort order changes
 * such that its position relative to its siblings changes. The `DataSnapshot`
 * passed to the callback will be for the data of the child that has moved. It
 * is also passed a second argument which is a string containing the key of the
 * previous sibling child by sort order, or `null` if it is the first child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildMoved(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildMoved` event will be triggered when a child's sort order changes
 * such that its position relative to its siblings changes. The `DataSnapshot`
 * passed to the callback will be for the data of the child that has moved. It
 * is also passed a second argument which is a string containing the key of the
 * previous sibling child by sort order, or `null` if it is the first child.
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildMoved(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, cancelCallback: (error: Error) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildRemoved` event will be triggered once every time a child is
 * removed. The `DataSnapshot` passed into the callback will be the old data for
 * the child that was removed. A child will get removed when either:
 *
 * - a client explicitly calls `remove()` on that child or one of its ancestors
 * - a client calls `set(null)` on that child or one of its ancestors
 * - that child has all of its children removed
 * - there is a query in effect which now filters out the child (because it's
 *   sort order changed or the max limit was hit)
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildRemoved(query: Query, callback: (snapshot: DataSnapshot) => unknown, cancelCallback?: (error: Error) => unknown): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildRemoved` event will be triggered once every time a child is
 * removed. The `DataSnapshot` passed into the callback will be the old data for
 * the child that was removed. A child will get removed when either:
 *
 * - a client explicitly calls `remove()` on that child or one of its ancestors
 * - a client calls `set(null)` on that child or one of its ancestors
 * - that child has all of its children removed
 * - there is a query in effect which now filters out the child (because it's
 *   sort order changed or the max limit was hit)
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildRemoved(query: Query, callback: (snapshot: DataSnapshot) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onChildRemoved` event will be triggered once every time a child is
 * removed. The `DataSnapshot` passed into the callback will be the old data for
 * the child that was removed. A child will get removed when either:
 *
 * - a client explicitly calls `remove()` on that child or one of its ancestors
 * - a client calls `set(null)` on that child or one of its ancestors
 * - that child has all of its children removed
 * - there is a query in effect which now filters out the child (because it's
 *   sort order changed or the max limit was hit)
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs.
 * The callback will be passed a DataSnapshot and a string containing the key of
 * the previous child, by sort order, or `null` if it is the first child.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onChildRemoved(query: Query, callback: (snapshot: DataSnapshot) => unknown, cancelCallback: (error: Error) => unknown, options: ListenOptions): Unsubscribe;
/**
 * The `onDisconnect` class allows you to write or clear data when your client
 * disconnects from the Database server. These updates occur whether your
 * client disconnects cleanly or not, so you can rely on them to clean up data
 * even if a connection is dropped or a client crashes.
 *
 * The `onDisconnect` class is most commonly used to manage presence in
 * applications where it is useful to detect how many clients are connected and
 * when other clients disconnect. See
 * {@link https://firebase.google.com/docs/database/web/offline-capabilities | Enabling Offline Capabilities in JavaScript}
 * for more information.
 *
 * To avoid problems when a connection is dropped before the requests can be
 * transferred to the Database server, these functions should be called before
 * writing any data.
 *
 * Note that `onDisconnect` operations are only triggered once. If you want an
 * operation to occur each time a disconnect occurs, you'll need to re-establish
 * the `onDisconnect` operations each time you reconnect.
 */
export declare class OnDisconnect {
    private constructor();
    /**
     * Cancels all previously queued `onDisconnect()` set or update events for this
     * location and all children.
     *
     * If a write has been queued for this location via a `set()` or `update()` at a
     * parent location, the write at this location will be canceled, though writes
     * to sibling locations will still occur.
     *
     * @returns Resolves when synchronization to the server is complete.
     */
    cancel(): Promise<void>;
    /**
     * Ensures the data at this location is deleted when the client is disconnected
     * (due to closing the browser, navigating to a new page, or network issues).
     *
     * @returns Resolves when synchronization to the server is complete.
     */
    remove(): Promise<void>;
    /**
     * Ensures the data at this location is set to the specified value when the
     * client is disconnected (due to closing the browser, navigating to a new page,
     * or network issues).
     *
     * `set()` is especially useful for implementing "presence" systems, where a
     * value should be changed or cleared when a user disconnects so that they
     * appear "offline" to other users. See
     * {@link https://firebase.google.com/docs/database/web/offline-capabilities | Enabling Offline Capabilities in JavaScript}
     * for more information.
     *
     * Note that `onDisconnect` operations are only triggered once. If you want an
     * operation to occur each time a disconnect occurs, you'll need to re-establish
     * the `onDisconnect` operations each time.
     *
     * @param value - The value to be written to this location on disconnect (can
     * be an object, array, string, number, boolean, or null).
     * @returns Resolves when synchronization to the Database is complete.
     */
    set(value: unknown): Promise<void>;
    /**
     * Ensures the data at this location is set to the specified value and priority
     * when the client is disconnected (due to closing the browser, navigating to a
     * new page, or network issues).
     *
     * @param value - The value to be written to this location on disconnect (can
     * be an object, array, string, number, boolean, or null).
     * @param priority - The priority to be written (string, number, or null).
     * @returns Resolves when synchronization to the Database is complete.
     */
    setWithPriority(value: unknown, priority: number | string | null): Promise<void>;
    /**
     * Writes multiple values at this location when the client is disconnected (due
     * to closing the browser, navigating to a new page, or network issues).
     *
     * The `values` argument contains multiple property-value pairs that will be
     * written to the Database together. Each child property can either be a simple
     * property (for example, "name") or a relative path (for example, "name/first")
     * from the current location to the data to update.
     *
     * As opposed to the `set()` method, `update()` can be use to selectively update
     * only the referenced properties at the current location (instead of replacing
     * all the child properties at the current location).
     *
     * @param values - Object containing multiple values.
     * @returns Resolves when synchronization to the Database is complete.
     */
    update(values: object): Promise<void>;
}
/**
 * Returns an `OnDisconnect` object - see
 * {@link https://firebase.google.com/docs/database/web/offline-capabilities | Enabling Offline Capabilities in JavaScript}
 * for more information on how to use it.
 *
 * @param ref - The reference to add OnDisconnect triggers for.
 */
export declare function onDisconnect(ref: DatabaseReference): OnDisconnect;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onValue` event will trigger once with the initial data stored at this
 * location, and then trigger again each time the data changes. The
 * `DataSnapshot` passed to the callback will be for the location at which
 * `on()` was called. It won't trigger until the entire contents has been
 * synchronized. If the location has no data, it will be triggered with an empty
 * `DataSnapshot` (`val()` will return `null`).
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs. The
 * callback will be passed a DataSnapshot.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onValue(query: Query, callback: (snapshot: DataSnapshot) => unknown, cancelCallback?: (error: Error) => unknown): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onValue` event will trigger once with the initial data stored at this
 * location, and then trigger again each time the data changes. The
 * `DataSnapshot` passed to the callback will be for the location at which
 * `on()` was called. It won't trigger until the entire contents has been
 * synchronized. If the location has no data, it will be triggered with an empty
 * `DataSnapshot` (`val()` will return `null`).
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs. The
 * callback will be passed a DataSnapshot.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onValue(query: Query, callback: (snapshot: DataSnapshot) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Listens for data changes at a particular location.
 *
 * This is the primary way to read data from a Database. Your callback
 * will be triggered for the initial data and again whenever the data changes.
 * Invoke the returned unsubscribe callback to stop receiving updates. See
 * {@link https://firebase.google.com/docs/database/web/retrieve-data | Retrieve Data on the Web}
 * for more details.
 *
 * An `onValue` event will trigger once with the initial data stored at this
 * location, and then trigger again each time the data changes. The
 * `DataSnapshot` passed to the callback will be for the location at which
 * `on()` was called. It won't trigger until the entire contents has been
 * synchronized. If the location has no data, it will be triggered with an empty
 * `DataSnapshot` (`val()` will return `null`).
 *
 * @param query - The query to run.
 * @param callback - A callback that fires when the specified event occurs. The
 * callback will be passed a DataSnapshot.
 * @param cancelCallback - An optional callback that will be notified if your
 * event subscription is ever canceled because your client does not have
 * permission to read this data (or it had permission but has now lost it).
 * This callback will be passed an `Error` object indicating why the failure
 * occurred.
 * @param options - An object that can be used to configure `onlyOnce`, which
 * then removes the listener after its first invocation.
 * @returns A function that can be invoked to remove the listener.
 */
export declare function onValue(query: Query, callback: (snapshot: DataSnapshot) => unknown, cancelCallback: (error: Error) => unknown, options: ListenOptions): Unsubscribe;
/**
 * Creates a new `QueryConstraint` that orders by the specified child key.
 *
 * Queries can only order by one key at a time. Calling `orderByChild()`
 * multiple times on the same query is an error.
 *
 * Firebase queries allow you to order your data by any child key on the fly.
 * However, if you know in advance what your indexes will be, you can define
 * them via the .indexOn rule in your Security Rules for better performance. See
 * the{@link https://firebase.google.com/docs/database/security/indexing-data}
 * rule for more information.
 *
 * You can read more about `orderByChild()` in
 * {@link https://firebase.google.com/docs/database/web/lists-of-data#sort_data | Sort da