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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).

A DataSnapshot is an efficiently generated, immutable copy of the data at a Database location. It cannot be modified and will never change (to modify data, you always call the set() method on a Reference directly).

Index

Properties

key

key: string | null

ref

Methods

child

  • 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.

    example
    // Assume we have the following data in the Database:
    {
      "name": {
        "first": "Ada",
        "last": "Lovelace"
      }
    }
    
    // Test for the existence of certain keys within a DataSnapshot
    var ref = admin.database().ref("users/ada");
    ref.once("value")
      .then(function(snapshot) {
        var name = snapshot.child("name").val