database.DataSnapshot class

Interface representing a Firebase Realtime database data snapshot.

Signature:

export declare class DataSnapshot implements database.DataSnapshot

Implements: database.DataSnapshot

Constructors

Constructor Modifiers Description
(constructor)(data, path, app, instance) Constructs a new instance of the DataSnapshot class

Properties

Property Modifiers Type Description
instance string
key string | 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 returns the key for the location that generated it. However, accessing the key on the root URL of a database returns null.
ref database.Reference Returns a [Reference](/docs/reference/admin/node/admin.database.Reference) to the database location where the triggering write occurred. Has full read and write access.

Methods

Method Modifiers Description
child(childPath) Gets a 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").
exists() Returns true if this DataSnapshot contains any data. It is slightly more efficient than using snapshot.val() !== null. true if this DataSnapshot contains any data; otherwise, false.
exportVal() Exports the entire contents of the DataSnapshot as a JavaScript object. The contents of the DataSnapshot as a JavaScript value (Object, Array, string, number, boolean, or null).
forEach(action) Enumerates the DataSnapshots of the children items.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 child_added events. That is where forEach() comes in handy. It guarantees the children of a DataSnapshot can 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).
getPriority() Gets the priority value of the data in this DataSnapshot.As an alternative to using priority, applications can order collections by ordinary properties. See [Sorting and filtering data](/docs/database/web/lists-of-data#sorting_and_filtering_data). The priority value of the data.
hasChild(childPath) Returns true if the specified child path has (non-null) data.
hasChildren() 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() returns null). true if this snapshot has any children; else false.
numChildren() Returns the number of child properties of this DataSnapshot. Number of child properties of this DataSnapshot.
toJSON() Returns a JSON-serializable representation of this object. A JSON-serializable representation of this object.
val() 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). The snapshot's contents as a JavaScript value (Object, Array, string, number, boolean, or null).

database.DataSnapshot.(constructor)

Constructs a new instance of the DataSnapshot class

Signature:

constructor(data: any, path?: string, // path is undefined for the database root
    app?: App, instance?: string);

Parameters

Parameter Type Description
data any
path string
app App
instance string

database.DataSnapshot.instance

Signature:

instance: string;

database.DataSnapshot.key

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 returns the key for the location that generated it. However, accessing the key on the root URL of a database returns null.

Signature:

get key(): string | null;

database.DataSnapshot.ref

Returns a [Reference](/docs/reference/admin/node/admin.database.Reference) to the database location where the triggering write occurred. Has full read and write access.

Signature:

get ref(): database.Reference;

database.DataSnapshot.child()

Gets a 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").

Signature:

child(childPath: string): DataSnapshot;

Parameters

Parameter Type Description
childPath string

Returns:

DataSnapshot

database.DataSnapshot.exists()

Returns true if this DataSnapshot contains any data. It is slightly more efficient than using snapshot.val() !== null.

true if this DataSnapshot contains any data; otherwise, false.

Signature:

exists(): boolean;

Returns:

boolean

database.DataSnapshot.exportVal()

Exports the entire contents of the DataSnapshot as a JavaScript object.

The contents of the DataSnapshot as a JavaScript value (Object, Array, string, number, boolean, or null).

Signature:

exportVal(): any;

Returns:

any

database.DataSnapshot.forEach()

Enumerates the DataSnapshots of the children items.

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 child_added events. That is where forEach() comes in handy. It guarantees the children of a DataSnapshot can 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).

Signature:

forEach(action: (a: IteratedDataSnapshot) => boolean | void): boolean;

Parameters

Parameter Type Description
action (a: IteratedDataSnapshot) => boolean | void A function that is called for each child DataSnapshot. The callback can return true to cancel further enumeration. true if enumeration was canceled due to your callback returning true.

Returns:

boolean

database.DataSnapshot.getPriority()

Gets the priority value of the data in this DataSnapshot.

As an alternative to using priority, applications can order collections by ordinary properties. See [Sorting and filtering data](/docs/database/web/lists-of-data#sorting_and_filtering_data).

The priority value of the data.

Signature:

getPriority(): string | number | null;

Returns:

string | number | null

database.DataSnapshot.hasChild()

Returns true if the specified child path has (non-null) data.

Signature:

hasChild(childPath: string): boolean;

Parameters

Parameter Type Description
childPath string

Returns:

boolean

database.DataSnapshot.hasChildren()

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() returns null).

true if this snapshot has any children; else false.

Signature:

hasChildren(): boolean;

Returns:

boolean

database.DataSnapshot.numChildren()

Returns the number of child properties of this DataSnapshot.

Number of child properties of this DataSnapshot.

Signature:

numChildren(): number;

Returns:

number

database.DataSnapshot.toJSON()

Returns a JSON-serializable representation of this object.

A JSON-serializable representation of this object.

Signature:

toJSON(): Record<string, unknown>;

Returns:

Record<string, unknown>

database.DataSnapshot.val()

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).

The snapshot's contents as a JavaScript value (Object, Array, string, number, boolean, or null).

Signature:

val(): any;

Returns:

any