React Native Firebase
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    Interface Reference

    A Reference 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 firebase.database().ref() or firebase.database().ref("child/path").

    interface Reference {
        key: string | null;
        parent: FirebaseDatabaseTypes.Reference | null;
        ref: FirebaseDatabaseTypes.Reference;
        root: FirebaseDatabaseTypes.Reference;
        child(path: string): FirebaseDatabaseTypes.Reference;
        endAt(
            value: string | number | boolean | null,
            key?: string,
        ): FirebaseDatabaseTypes.Query;
        equalTo(
            value: string | number | boolean | null,
            key?: string,
        ): FirebaseDatabaseTypes.Query;
        isEqual(other: FirebaseDatabaseTypes.Query): boolean;
        keepSynced(bool: boolean): Promise<void>;
        limitToFirst(limit: number): FirebaseDatabaseTypes.Query;
        limitToLast(limit: number): FirebaseDatabaseTypes.Query;
        off(
            eventType?: EventType,
            callback?: (
                a: FirebaseDatabaseTypes.DataSnapshot,
                b?: string | null,
            ) => void,
            context?: Record<string, any>,
        ): void;
        on(
            eventType: EventType,
            callback: (
                data: FirebaseDatabaseTypes.DataSnapshot,
                previousChildKey?: string | null,
            ) => void,
            cancelCallbackOrContext?:
                | Record<string, any>
                | ((a: Error) => void)
                | null,
            context?: Record<string, any> | null,
        ): (
            a: FirebaseDatabaseTypes.DataSnapshot | null,
            b?: string | null,
        ) => void;
        once(
            eventType: EventType,
            successCallback?: (
                a: FirebaseDatabaseTypes.DataSnapshot,
                b?: string | null,
            ) => any,
            failureCallbackContext?: Record<string, any> | ((a: Error) => void) | null,
        ): Promise<FirebaseDatabaseTypes.DataSnapshot>;
        onDisconnect(): FirebaseDatabaseTypes.OnDisconnect;
        orderByChild(path: string): FirebaseDatabaseTypes.Query;
        orderByKey(): FirebaseDatabaseTypes.Query;
        orderByPriority(): FirebaseDatabaseTypes.Query;
        orderByValue(): FirebaseDatabaseTypes.Query;
        push(value?: any, onComplete?: () => void): FirebaseDatabaseTypes.Reference;
        remove(onComplete?: (error: Error | null) => void): Promise<void>;
        set(value: any, onComplete?: (error: Error | null) => void): Promise<void>;
        setPriority(
            priority: string | number | null,
            onComplete?: (error: Error | null) => void,
        ): Promise<void>;
        setWithPriority(
            newVal: any,
            newPriority: string | number | null,
            onComplete?: (error: Error | null) => void,
        ): Promise<void>;
        startAt(
            value: string | number | boolean | null,
            key?: string,
        ): FirebaseDatabaseTypes.Query;
        toJSON(): object;
        toString(): string;
        transaction(
            transactionUpdate: (currentData: any) => any,
            onComplete?: (
                error: Error | null,
                committed: boolean,
                finalResult: FirebaseDatabaseTypes.DataSnapshot,
            ) => void,
            applyLocally?: boolean,
        ): Promise<FirebaseDatabaseTypes.TransactionResult>;
        update(
            values: { [key: string]: any },
            onComplete?: (error: Error | null) => void,
        ): Promise<void>;
    }

    Hierarchy (View Summary)

    Index

    Methods

    child endAt equalTo isEqual keepSynced limitToFirst limitToLast off on once onDisconnect orderByChild orderByKey orderByPriority orderByValue push remove set setPriority setWithPriority startAt toJSON toString transaction update

    Properties

    key parent ref root

    Methods

    • 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").

      const usersRef = firebase.database().ref('users');
      const adaRef = usersRef.child('ada/name/first'); // childRef path is 'users/ada/name/first'

      Parameters

      • path: string

        A relative path from this location to the desired child location.

      Returns FirebaseDatabaseTypes.Reference

    • Creates a Query with the specified ending point.

      Using startAt(), 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 Filtering data.

      const ref = firebase.database().ref('users');
      const snapshot = await ref.orderByKey().endAt('Ada Lovelace').once('value');

      Parameters

      • value: string | number | boolean | null

        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.

      • Optionalkey: string

        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.

      Returns FirebaseDatabaseTypes.Query

    • Creates a Query with the specified ending point.

      Using startAt(), 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 Filtering data.

      const ref = firebase.database().ref('users');
      const snapshot = await ref.orderByChild('age').equalTo(30).once('value');

      Parameters

      • value: string | number | boolean | null

        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.

      • Optionalkey: string

        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.

      Returns FirebaseDatabaseTypes.Query

    • Returns whether or not the current and provided queries represent the same location, have the same query parameters.

      Two Reference objects are equivalent if they represent the same location and are from the same instance of @firebase/app!FirebaseApp. Equivalent queries share the same sort order, limits, and starting and ending points.

      const ref1 = firebase.database().ref('users').orderByKey().endAt('Ada Lovelace');
      const ref2 = firebase.database().ref('users').orderByKey();

      console.log(ref1.isEqual(ref2)); // false

      const ref1 = firebase.database().ref('users').orderByKey().endAt('Ada Lovelace');
      const ref2 = firebase.database().ref('users').endAt('Ada Lovelace').orderByKey();

      console.log(ref1.isEqual(ref2)); // true

      Parameters

      Returns boolean

    • By calling keepSynced(true) on a location, the data for that location will automatically be downloaded and kept in sync, even when no listeners are attached for that location.

      const ref = firebase.database().ref('users');
      await ref.keepSynced(true);

      Parameters

      • bool: boolean

        Pass true to keep this location synchronized, pass false to stop synchronization.

      Returns Promise<void>

    • Generates a new Query 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 Filtering data.

      const snapshot = firebase.database().ref('users').orderByKey().limitToFirst(2).once('value');
      console.log(snapshot.numChildren()); // 2

      Parameters

      • limit: number

        The maximum number of nodes to include in this query.

      Returns FirebaseDatabaseTypes.Query

    • Generates a new Query object limited to the last specific 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 Filtering data.

      const snapshot = firebase.database().ref('users').orderByKey().limitToLast(2).once('value');
      console.log(snapshot.numChildren()); // 2

      Parameters

      • limit: number

        The maximum number of nodes to include in this query.

      Returns FirebaseDatabaseTypes.Query

    • Detaches a callback previously attached with on().

      Detach a callback previously attached with on(). Note that if on() was called multiple times with the same eventType and callback, the callback will be called multiple times for each event, and off() must be called multiple times to remove the callback. 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.

      const ref = firebase.database().ref('settings');
      const onValueChange = function(snapshot) { ... };
      const onChildAdded = function(snapshot) { ... };

      ref.on('value', onValueChange);
      ref.child('meta-data').on('child_added', onChildAdded);
      // Sometime later...
      ref.off('value', onValueChange);
      ref.child('meta-data').off('child_added', onChildAdded);

      Parameters

      • OptionaleventType: 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.

      • Optionalcallback: (a: FirebaseDatabaseTypes.DataSnapshot, b?: string | null) => void

        The callback function that was passed to on() or undefined to remove all callbacks.

      • Optionalcontext: Record<string, any>

        The context that was passed to on().

      Returns 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. Use off() to stop receiving updates..

      value event

      This 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).

      child_added event

      This 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.

      child_removed event

      This 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)

      child_changed event

      This 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.

      child_moved event

      This 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.

      Parameters

      • eventType: EventType

        One of the following strings: "value", "child_added", "child_changed", "child_removed", or "child_moved."

      • callback: (
            data: FirebaseDatabaseTypes.DataSnapshot,
            previousChildKey?: string | null,
        ) => void

        A callback that fires when the specified event occurs. The callback will be passed a DataSnapshot. For ordering purposes, "child_added", "child_changed", and "child_moved" will also be passed a string containing the key of the previous child, by sort order, or null if it is the first child.

      • OptionalcancelCallbackOrContext: Record<string, any> | ((a: Error) => void) | null

        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.

      • Optionalcontext: Record<string, any> | null

        If provided, this object will be used as this when calling your callback(s).

      Returns (a: FirebaseDatabaseTypes.DataSnapshot | null, b?: string | null) => void

    • Listens for exactly one event of the specified event type, and then stops listening.

      This is equivalent to calling on(), and then calling off() inside the callback function. See on() for details on the event types.

      // Promise
      const snapshot = await firebase.database().ref('users').once('value');
      // Callback
      firebase.database().ref('users).once('value', (snapshot) => {
        console.log(snapshot.val());
      });

      Parameters

      • eventType: EventType

        One of the following strings: "value", "child_added", "child_changed", "child_removed", or "child_moved."

      • OptionalsuccessCallback: (a: FirebaseDatabaseTypes.DataSnapshot, b?: string | null) => any

        A callback that fires when the specified event occurs. The callback will be passed a DataSnapshot. For ordering purposes, "child_added", "child_changed", and "child_moved" will also be passed a string containing the key of the previous child by sort order, or null if it is the first child.

      • OptionalfailureCallbackContext: Record<string, any> | ((a: Error) => void) | null

        An optional callback that will be notified if your client does not have permission to read the data. This callback will be passed an Error object indicating why the failure occurred.

      Returns Promise<FirebaseDatabaseTypes.DataSnapshot>

    • Generates a new Query object ordered 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.

      You can read more about orderByChild() in Sort data.

      const snapshot = await firebase.database().ref('users').orderByChild('age').once('value');
      snapshot.forEach((snapshot) => {
       console.log('Users age:', snapshot.val().age);
      });

      Parameters

      • path: string

        The child path node to order by.

      Returns FirebaseDatabaseTypes.Query

    • Generates a new Query object ordered by key.

      Sorts the results of a query by their (ascending) key values.

      You can read more about orderByKey() in Sort data.

      const snapshot = await firebase.database().ref('users').orderByKey().once('value');
      snapshot.forEach((snapshot) => {
       console.log('User:', snapshot.val());
      });

      Returns FirebaseDatabaseTypes.Query

    • Generates a new child location using a unique key and returns its Reference.

      This is the most common pattern for adding data to a collection of items.

      If you provide a value to push(), the value will be written to the generated location. If you don't pass a value, nothing will be written to the Database and the child will remain empty (but you can use the Reference elsewhere).

      The unique key generated by push() are ordered by the current time, so the resulting list of items will be chronologically sorted. The keys are also designed to be unguessable (they contain 72 random bits of entropy).

      const newUserRef = firebase.database().ref('users').push();
      console.log('New record key:', newUserRef.key);
      await newUserRef.set({
        first: 'Ada',
        last: 'Lovelace',
      });

      Parameters

      • Optionalvalue: any

        Optional value to be written at the generated location.

      • OptionalonComplete: () => void

        Callback called when write to server is complete.

      Returns FirebaseDatabaseTypes.Reference

    • Removes the data at this Database location.

      Any data at child locations will also be deleted.

      The effect of the remove will be visible immediately and the corresponding event 'value' will be triggered. Synchronization of the remove to the Firebase servers will also be started, and the returned Promise will resolve when complete. If provided, the onComplete callback will be called asynchronously after synchronization has finished.

      await firebase.database().ref('users/ada/name')
       .remove(() => {
         console.log('Operation Complete');
       });

      Parameters

      • OptionalonComplete: (error: Error | null) => void

        Callback called when write to server is complete. Contains the parameters (Error | null).

      Returns Promise<void>

    • Writes data to this Database location.

      This will overwrite any data at this location and all child locations.

      The effect of the write will be visible immediately, and the corresponding events ("value", "child_added", etc.) will be triggered. Synchronization of the data to the Firebase servers will also be started, and the returned Promise will resolve when complete. If provided, the onComplete callback will be called asynchronously after synchronization has finished.

      Passing null for the new value is equivalent to calling remove(); namely, all data at this location and all child locations will be deleted.

      set() will remove any priority stored at this location, so if priority is meant to be preserved, you need to use setWithPriority() instead.

      Note that modifying data with set() will cancel any pending transactions at that location, so extreme care should be taken if mixing set() and transaction() to modify the same data.

      A single set() will generate a single "value" event at the location where the set() was performed.

      const ref = firebase.database().ref('users');

      // Set a single node value
      await ref.child('ada/name/first').set('Ada');
      await ref.child('ada/name/last').set('Lovelace');

      // Set an object value in a single call
      await ref.child('ada/name').set({
        first: 'Ada',
        last: 'Lovelace',
      });

      const ref = firebase.database().ref('users');

      await ref.child('ada/first/name').set('Ada', (error) => {
        if (error) console.error(error);
      });

      Parameters

      • value: any

        The value to be written (string, number, boolean, object, array, or null).

      • OptionalonComplete: (error: Error | null) => void

        Callback called when write to server is complete. Contains the parameters (Error | null).

      Returns Promise<void>

    • Sets a priority for the data at this Database location. Setting null removes any priority at this location.

      See Query#orderByPriority to learn how to use priority values in your query.

      await firebase.database().ref('users/ada').setPriority(1, (error) => {
        if (error) console.error(error);
      });

      Parameters

      • priority: string | number | null

        The priority value.

      • OptionalonComplete: (error: Error | null) => void

        Callback called when write to server is complete. Contains the parameters (Error | null).

      Returns Promise<void>

    • Writes data the Database location. Like set() but also specifies the priority for that data.

      await firebase.database().ref('users/ada/name')
       .setWithPriority({
         first: 'Ada',
         last: 'Lovelace',
       }, 1, (error) => {
         if (error) console.error(error);
       });

      Parameters

      • newVal: any

        The new value to set.

      • newPriority: string | number | null

        The new priority to set.

      • OptionalonComplete: (error: Error | null) => void

        Callback called when write to server is complete. Contains the parameters (Error | null).

      Returns Promise<void>

    • Creates a Query with the specified starting point.

      Using startAt(), endAt(), and equalTo() allows you to choose arbitrary starting and ending points for your queries.

      The starting 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 greater than or equal to the specified key.

      You can read more about startAt() in Filtering data.

      await firebase.database().ref('users').orderByChild('age').startAt(21).once('value');

      Parameters

      • value: string | number | boolean | null

        The value to start 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.

      • Optionalkey: string

        The child key to start at. This argument is only allowed if ordering by child, value, or priority.

      Returns FirebaseDatabaseTypes.Query

    • Returns a JSON-serializable representation of this object.

      Returns object

    • Gets the absolute URL for this location.

      The toString() method returns a URL that is ready to be put into a browser, curl command, or a firebase.database().refFromURL() call. Since all of those expect the URL to be url-encoded, toString() returns an encoded URL.

      Append '.json' to the returned URL when typed into a browser to download JSON-formatted data. If the location is secured (that is, not publicly readable), you will get a permission-denied error.

      const ref1 = firebase.database().ref();
      const ref2 = firebase.database().ref('users').orderByValue();

      ref1.toString(); // https://sample-app.firebaseio.com/
      ref2.toString(); // https://sample-app.firebaseio.com/users

      Returns string

    • Atomically modifies the data at this location.

      Atomically modify the data at this location. Unlike a normal set(), which just overwrites the data regardless of its previous value, transaction() is used to modify the existing value to a new value, ensuring there are no conflicts with other clients writing to the same location at the same time.

      To accomplish this, you pass transaction() an update function which is used to transform the current value into a new value. If another client writes to the location before your new value is successfully written, your update function will be called again with the new current value, and the write will be retried. This will happen repeatedly until your write succeeds without conflict or you abort the transaction by not returning a value from your update function.

      Note: Modifying data with set() will cancel any pending transactions at that location, so extreme care should be taken if mixing set() and transaction() to update the same data.

      Note: When using transactions with Security and Firebase Rules in place, be aware that a client needs .read access in addition to .write access in order to perform a transaction. This is because the client-side nature of transactions requires the client to read the data in order to transactionally update it.

      const userRef = firebase.database().ref('users/ada/profileViews);

      userRef.transaction((currentViews) => {
        if (currentViews === null) return 1;
        return currentViews + 1;
      });

      Parameters

      • transactionUpdate: (currentData: any) => any

        A developer-supplied function which will be passed the current data stored at this location (as a JavaScript object). The function should return the new value it would like written (as a JavaScript object). If undefined is returned (i.e. you return with no result) the transaction will be aborted and the data at this location will not be modified.

      • OptionalonComplete: (
            error: Error | null,
            committed: boolean,
            finalResult: FirebaseDatabaseTypes.DataSnapshot,
        ) => void

        A callback function that will be called when the transaction completes. The callback is passed three arguments: a possibly-null Error, a boolean indicating whether the transaction was committed, and a DataSnapshot indicating the final result. If the transaction failed abnormally, the first argument will be an Error object indicating the failure cause. If the transaction finished normally, but no data was committed because no data was returned from transactionUpdate, then second argument will be false. If the transaction completed and committed data to Firebase, the second argument will be true. Regardless, the third argument will be a DataSnapshot containing the resulting data in this location.

      • OptionalapplyLocally: boolean

        By default, events are raised each time the transaction update function runs. So if it is run multiple times, you may see intermediate states. You can set this to false to suppress these intermediate states and instead wait until the transaction has completed before events are raised.

      Returns Promise<FirebaseDatabaseTypes.TransactionResult>

    • Writes multiple values to the Database at once.

      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).

      The effect of the write will be visible immediately, and the corresponding events ('value', 'child_added', etc.) will be triggered. Synchronization of the data to the Firebase servers will also be started, and the returned Promise will resolve when complete. If provided, the onComplete callback will be called asynchronously after synchronization has finished.

      A single update() will generate a single "value" event at the location where the update() was performed, regardless of how many children were modified.

      Note that modifying data with update() will cancel any pending transactions at that location, so extreme care should be taken if mixing update() and transaction() to modify the same data.

      Passing null to update() will remove the data at this location.

      Modify the 'first' and 'last' properties, but leave other values unchanged at this location.

      await firebase.database().ref('users/ada/name').update({
        first: 'Ada',
        last: 'Lovelace',
      })

      Parameters

      • values: { [key: string]: any }

        Object containing multiple values.

      • OptionalonComplete: (error: Error | null) => void

        Callback called when write to server is complete. Contains the parameters (Error | null).

      Returns Promise<void>

    Properties

    key: string | null

    The last part of the Reference's path. For example, "ada" is the key for https://<DATABASE_NAME>.firebaseio.com/users/ada. The key of a root Reference is null.

    parent: FirebaseDatabaseTypes.Reference | null

    The parent location of a Reference. The parent of a root Reference is null.

    firebase.database().ref().parent; // null
    firebase.database().ref('users/dave').parent; // 'users' reference
    ref: FirebaseDatabaseTypes.Reference

    Returns a Reference to the Query's location.

    root: FirebaseDatabaseTypes.Reference

    The root Reference of the Database.

    firebase.database().ref().root; // '/' reference path
    firebase.database().ref('users/ada').root; // '/' reference

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