JSDoc: Class: DataSnapshot

Example

var ref = new Webcom("contacts").child("friends/john");
ref.once("value", snapshot => {
  // Your code
  // snapshot.val() returns the data associated with snapshot, that is, the data at the "friends/john" data node
});

Methods

acknowledged() → {boolean}

Returns the source of the data wrapped by this DataSnapshot instance among. true means the data is acknowledged by the back end, false means the data is purely local.

Returns:

Type: boolean

child(childPathString) → {DataSnapshot}

Retrieve child DataSnapshot corresponding to specified relative path

Parameters:

Name	Type	Description
`childPathString`	String	relative path

Returns:

child DataSnapshot

Type: DataSnapshot

Example

// Get a reference to John
var ref = new Webcom("contacts").child("friends/john");

ref.once("value", function(snapshot){
 var nameSnapshot = snapshot.child("name");
 var name = nameSnapshot.val();
 console.log(name);
 // ==> { first: "John", last: "Doe" }

 var firstName = snapshot.child("name/first").val();
 //Or
 var firstName = nameSnapshot.child("first");
 // It's like you do snapshot.child("name").child("first");
 console.log(firstName.val());
 // ==> John

 var mobilePhone = snapshot.child("mobilePhone");
 console.log(mobilePhone.val());
 // ==> null (There is no "mobilePhone" child)
});

eventType() → {string}

Returns the event type that produced this DataSnapshot instance, when it results from the Query.on method. Otherwise, this property remains undefined.

Returns:

Type: string

exportVal() → {*}

Retrieve value object of the DataSnapshot with all its metadata.

Returns:

DataSnapshot value object with metadata

Type: *

Example

// Get a reference to our contacts
 var ref = new Webcom("contacts").child("friends");

 // Iterates over all friends with metadata
 ref.set({ name: "John" }, function(error){
     ref.on("value", function(snapshot) {
         var user = snapshot.exportVal();
         // Display information of current user
         console.log(user.first_name);
         //David
     });
 });

forEach(action) → {Boolean}

Iterate over DataSnapshot's children

Parameters:

Name	Type	Description
`action`	function	For each child, this function is called with child as parameter. You can return `true` to stop loop.

Returns:

true if loop was stopped intentionally.

Type: Boolean

Example

// Get a reference to friends
var ref = new Webcom("contacts").child("friends");

ref.once("value", function(snapshot){
 // Callback function will get called once per user found
 snapshot.forEach(function(childSnapshot){
     // key contains key value of occurrence, per example "john"
     var key = childSnapshot.name();

     // childData will be current value of the child
     var childData = childSnapshot.val()
     // childData ==> { first: "John", last: "Doe" }

     //If you want you can cancel the enumeration with a return true
     //It's useful for a search function for example
     return true;
 });
});

hasChild(childPathString) → {Boolean}

Returns if specified child exists

Parameters:

Name	Type	Description
`childPathString`	String	relative path

Returns:

true if child exists, false otherwise

Type: Boolean

Example

// Get a reference to John
var ref = new Webcom("contacts").child("friends/john");

ref.once("value", function(snapshot){
 var hasNameChild = snapshot.hasChild("name");
 // hasNameChild ==> true

 var hasMobilePhoneChild = snapshot.child("mobilePhone");
 // hasMobilePhoneChild ==> false
});

hasChildren() → {Boolean}

Returns if current DataSnapshot has at least one child.

Returns:

true if any child exists, false otherwise

Type: Boolean

Example

// Get a reference to John
var ref = new Webcom("contacts").child("friends/john");

ref.once("value", function(snapshot){
 var johnHasChildren = snapshot.hasChildren();
 // johnHasChildren ==> true

 var nameHasChildren = snapshot.child("name").hasChildren();
 // nameHasChildren ==> true

 var firstHasChildren = snapshot.child("name").child("first").hasChildren();
 // firstHasChildren ==> false ; a string doesn't have children
});

name() → {String}

Retrieve key of current location targeted by DataSnapshot

Returns:

key name

Type: String

Examples

// Get a reference to John
var ref = new Webcom("contacts").child("friends/john");

ref.once("value", function(snapshot){
 var johnKey = snapshot.name();
 // johnKey ==> "john"

 var lastKey = snapshot.child("name").child("last");
 // lastKey ==> "last"
});

//Other example without nodes
var ref = new Webcom("contacts");

ref.once("value", function(snapshot){
 var rootKey = snapshot.name();
 // rootKey ==> null

 var johnKey = snapshot.child("friends/john");
 // lastKey ==> "john"
});

numChildren() → {Number}

Retrieve number of children

Returns:

number of children

Type: Number

Example

// Get a reference to John
var ref = new Webcom("contacts").child("friends/john");

ref.once("value", function(snapshot){
 var johnChildren = snapshot.numChildren();
 // johnChildren ==> 1 ("name")

 var nameChildren = snapshot.child("name").numChildren();
 // nameChildren ==> 3 ("last","first","address")

 var firstChildren = snapshot.child("name").child("first").numChildren();
 // firstChildren ==> 0 ; It's a string therefore there is no children
});

rawVal() → {Object|String|Number|Boolean|Null}

Retrieves the raw value of this DataSnapshot. The raw value is either a constant or a treelike value involving exclusively JSON objects (with no JSON array at any level).

See:

Returns:

value object

Type: Object | String | Number | Boolean | Null

Example

// Get a reference to our contacts
 var ref = new Webcom("contacts");

 // Display all contacts
 ref.once("value", function(snapshot) {
     console.log(snapshot.rawVal());
     // {"0": {"firstname": "john", "name": "doe"},
     //  "1": {"firstname": "david", "name": "smith"}}
 });

ref() → {Webcom}

Retrieve current Webcom instance for this DataSnapshot.

Returns:

{Webcom} instance

Type: Webcom

Example

// Get a reference to John
var ref = new Webcom("contacts").child("friends/john");

ref.once("value", function(snapshot){
 var snapshotRef = snapshot.ref();

 var snapshotRefJohn = snapshotRef.name();
 // snapshotRefJohn ==> "john"
 //snapshotRefJohn === snapshot.name()
});

val() → {Object|String|Number|Boolean|Null}

Retrieves the value of this DataSnapshot as a JSON value. Subtrees whose keys are integer values are returned as JSON arrays.

See:

rawVal

Returns:

value object

Type: Object | String | Number | Boolean | Null

Example

// Get a reference to our contacts
 var ref = new Webcom("contacts");

 // Display all contacts
 ref.once("value", function(snapshot) {
     console.log(snapshot.val());
     // [{"firstname": "John", "name": "Doe"}, {"firstname": "Robert", "name": "Martin"}]
 });