TheonDisconnect class allows you to write or clear data when your clientdisconnects from the Database server. These updates occur whether yourclient disconnects cleanly or not, so you can rely on them to clean up dataeven if a connection is dropped or a client crashes.

TheonDisconnect class is most commonly used to manage presence inapplications where it is useful to detect how many clients are connected andwhen other clients disconnect. See Enabling Offline Capabilities in JavaScript for more information.

To avoid problems when a connection is dropped before the requests can betransferred to the Database server, these functions should be called beforewriting any data.

Note thatonDisconnect operations are only triggered once. If you want anoperation to occur each time a disconnect occurs, you'll need to re-establishtheonDisconnect operations each time you reconnect.

Index

Methods

cancel

  • cancel(onComplete?: (a: Error |null) =>any):Promise<any>

  • Cancels all previously queuedonDisconnect() set or update events for thislocation and all children.

    If a write has been queued for this location via aset() orupdate() at aparent location, the write at this location will be canceled, though writesto sibling locations will still occur.

    example
    var ref = firebase.database().ref("onlineState");ref.onDisconnect().set(false);// ... sometime laterref.onDisconnect().cancel();

    Parameters

    • Optional onComplete:(a:Error |null) =>any

      An optional callback function that willbe called when synchronization to the server has completed. The callbackwill be passed a single parameter: null for success, or an Error objectindicating a failure.

        • Parameters

          Returnsany

    ReturnsPromise<any>

    Resolves when synchronization to the serveris complete.

remove

  • remove(onComplete?: (a: Error |null) =>any):Promise<any>

  • 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).

    Parameters

    • Optional onComplete:(a:Error |null) =>any

      An optional callback function that willbe called when synchronization to the server has completed. The callbackwill be passed a single parameter: null for success, or an Error objectindicating a failure.

        • Parameters

          Returnsany

    ReturnsPromise<any>

    Resolves when synchronization to the serveris complete.

set

  • set(value: any, onComplete?: (a: Error |null) =>any):Promise<any>

  • Ensures the data at this location is set to the specified value when theclient is disconnected (due to closing the browser, navigating to a new page,or network issues).

    set() is especially useful for implementing "presence" systems, where avalue should be changed or cleared when a user disconnects so that theyappear "offline" to other users. See Enabling Offline Capabilities in JavaScript for more information.

    Note thatonDisconnect operations are only triggered once. If you want anoperation to occur each time a disconnect occurs, you'll need to re-establishtheonDisconnect operations each time.

    example
    var ref = firebase.database().ref("users/ada/status");ref.onDisconnect().set("I disconnected!");

    Parameters

    • value:any

      The value to be written to this location ondisconnect (can be an object, array, string, number, boolean, or null).

    • Optional onComplete:(a:Error |null) =>any

      An optional callback function thatwill be called when synchronization to the Database server has completed.The callback will be passed a single parameter: null for success, or anError object indicating a failure.

        • Parameters

          Returnsany

    ReturnsPromise<any>

    Resolves when synchronization to theDatabase is complete.

setWithPriority

  • setWithPriority(value: any, priority: number |string |null, onComplete?: (a: Error |null) =>any):Promise<any>

  • Ensures the data at this location is set to the specified value and prioritywhen the client is disconnected (due to closing the browser, navigating to anew page, or network issues).

    Parameters

    • value:any
    • priority:number |string |null
    • Optional onComplete:(a:Error |null) =>any

        • Parameters

          Returnsany

    ReturnsPromise<any>

update

  • update(values: Object, onComplete?: (a: Error |null) =>any):Promise<any>

  • Writes multiple values at this location when the client is disconnected (dueto closing the browser, navigating to a new page, or network issues).

    Thevalues argument contains multiple property-value pairs that will bewritten to the Database together. Each child property can either be a simpleproperty (for example, "name") or a relative path (for example, "name/first")from the current location to the data to update.

    As opposed to theset() method,update() can be use to selectively updateonly the referenced properties at the current location (instead of replacingall the child properties at the current location).

    See more examples using the connected version ofupdate().

    example
    var ref = firebase.database().ref("users/ada");ref.update({onlineState:true,status:"I'm online."});ref.onDisconnect().update({onlineState:false,status:"I'm offline."});

    Parameters

    • values:Object

      Object containing multiple values.

    • Optional onComplete:(a:Error |null) =>any

      An optional callback function that willbe called when synchronization to the server has completed. Thecallback will be passed a single parameter: null for success, or an Errorobject indicating a failure.

        • Parameters

          Returnsany

    ReturnsPromise<any>

    Resolves when synchronization to theDatabase is complete.

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Last updated 2022-07-27 UTC.