React Native Firebase
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    Interface DataSnapshot

    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).

    interface DataSnapshot {
        key: string | null;
        ref: FirebaseDatabaseTypes.Reference;
        child(path: string): FirebaseDatabaseTypes.DataSnapshot;
        exists(): boolean;
        exportVal(): any;
        forEach(
            action: (child: FirebaseDatabaseTypes.DataSnapshot) => true | undefined,
        ): boolean;
        getPriority(): string | number | null;
        hasChild(path: string): boolean;
        hasChildren(): boolean;
        numChildren(): number;
        toJSON(): object | null;
        val(): any;
    }
    Index

    Methods

    child exists exportVal forEach getPriority hasChild hasChildren numChildren toJSON val

    Properties

    key ref

    Methods

    • 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.

      const snapshot = await firebase.database().ref('users/ada').once('value');
      snapshot.child('name').val(); // {first:"Ada",last:"Lovelace"}
      snapshot.child('name/first').val(); // "Ada"
      snapshot.child('name/foo').val(); // null

      Parameters

      • path: string

        A relative path to the location of child data.

      Returns FirebaseDatabaseTypes.DataSnapshot

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

      const snapshot = await firebase.database().ref('users/ada').once('value');
      snapshot.exists(); // true
      snapshot.child('name/foo').exists(); // false

      Returns 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.

      const snapshot = await firebase.database().ref('users/ada').once('value');
      const data = snapshot.exportVal();
      console.log(data['.value']); // { ... }
      console.log(data['.priority']); // null

      Returns any

    • Enumerates the top-level children in the DataSnapshot.

      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 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).

      Parameters

      • action: (child: FirebaseDatabaseTypes.DataSnapshot) => true | undefined

        A function that will be called for each child DataSnapshot. The callback can return true to cancel further enumeration.

      Returns boolean

    • Gets the priority value of the data in this DataSnapshot.

      Returns string | number | null

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

      const snapshot = await firebase.database().ref('users/ada').once('value');
      console.log(snapshot.hasChild('name')); // true
      console.log(snapshot.hasChild('foo')); // false

      Parameters

      • path: string

        A relative path to the location of a potential child.

      Returns 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).

      const snapshot = await firebase.database().ref('users').once('value');
      console.log(snapshot.hasChildren()); // true

      Returns boolean

    • Returns the number of child properties of this DataSnapshot.

      Returns number

    • Returns a JSON-serializable representation of this object.

      Returns 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).

      const snapshot = await firebase.database().ref('users/ada/last').once('value');
      snapshot.val(); // "Lovelace"

      Returns any

    Properties

    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 will return the key for the location that generated it. However, accessing the key on the root URL of a Database will return null.

    ref: FirebaseDatabaseTypes.Reference

    The Reference for the location that generated this DataSnapshot.

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