[Home](./index.md) > [@firebase/database](./database.md) > [DataSnapshot](./database.datasnapshot.md) ## DataSnapshot class 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). Signature: ```typescript export declare class DataSnapshot ``` ## Properties | Property | Modifiers | Type | Description | | --- | --- | --- | --- | | [key](./database.datasnapshot.key.md) | | string \| null | The key (last part of the path) of the location of this DataSnapshot.The last token in a Database location is considered its key. For example, "ada" is the key for the /users/ada/ node. Accessing the key on any DataSnapshot will return the key for the location that generated it. However, accessing the key on the root URL of a Database will return null. | | [priority](./database.datasnapshot.priority.md) | | string \| number \| null | Gets the priority value of the data in this DataSnapshot.Applications need not use priority but can order collections by ordinary properties (see [Sorting and filtering data](https://firebase.google.com/docs/database/web/lists-of-data#sorting_and_filtering_data) ). | | [ref](./database.datasnapshot.ref.md) | | [Reference](./database.reference.md) | The location of this DataSnapshot. | | [size](./database.datasnapshot.size.md) | | number | Returns the number of child properties of this DataSnapshot. | ## Methods | Method | Modifiers | Description | | --- | --- | --- | | [child(path)](./database.datasnapshot.child.md) | | 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. | | [exists()](./database.datasnapshot.exists.md) | | Returns true if this DataSnapshot contains any data. It is slightly more efficient than using snapshot.val() !== null. | | [exportVal()](./database.datasnapshot.exportval.md) | | Exports the entire contents of the DataSnapshot as a JavaScript object.The exportVal() method is similar to val(), except priority information is included (if available), making it suitable for backing up your data. | | [forEach(action)](./database.datasnapshot.foreach.md) | | Enumerates the top-level children in the DataSnapshot.Because of the way JavaScript objects work, the ordering of data in the JavaScript object returned by val() is not guaranteed to match the ordering on the server nor the ordering of onChildAdded() events. That is where forEach() comes in handy. It guarantees the children of a DataSnapshot will be iterated in their query order.If no explicit orderBy*() method is used, results are returned ordered by key (unless priorities are used, in which case, results are returned by priority). | | [hasChild(path)](./database.datasnapshot.haschild.md) | | Returns true if the specified child path has (non-null) data. | | [hasChildren()](./database.datasnapshot.haschildren.md) | | Returns whether or not the DataSnapshot has any non-null child properties.You can use hasChildren() to determine if a DataSnapshot has any children. If it does, you can enumerate them using forEach(). If it doesn't, then either this snapshot contains a primitive value (which can be retrieved with val()) or it is empty (in which case, val() will return null). | | [toJSON()](./database.datasnapshot.tojson.md) | | Returns a JSON-serializable representation of this object. | | [val()](./database.datasnapshot.val.md) | | Extracts a JavaScript value from a DataSnapshot.Depending on the data in a DataSnapshot, the val() method may return a scalar type (string, number, or boolean), an array, or an object. It may also return null, indicating that the DataSnapshot is empty (contains no data). |