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onChildRemoved() function

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 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)

Signature:

export declare function onChildRemoved(query: Query, callback: (snapshot: DataSnapshot) => unknown, cancelCallback?: (error: Error) => unknown): Unsubscribe;

Parameters

Parameter	Type	Description
query	Query	The query to run.
callback	(snapshot: DataSnapshot) => unknown	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.
cancelCallback	(error: Error) => unknown	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:

Unsubscribe

A function that can be invoked to remove the listener.