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onChildMoved() 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 onChildMoved 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.

Signature:

export declare function onChildMoved(query: Query, callback: (snapshot: DataSnapshot, previousChildName: string | null) => unknown, cancelCallback?: (error: Error) => unknown): Unsubscribe;

Parameters

Parameter	Type	Description
query	Query	The query to run.
callback	(snapshot: DataSnapshot, previousChildName: string | null) => 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.