JavaScript, overwrite object without losing reference

JavaScript, overwrite object without losing reference

Application
I am working on a simple web application that is built on top of
AngularJS. The application should be able to work offline as well as
online. When the user is offline, the changes to the data is stored
locally. Therefore, the id's that is used within this application in
offline mode is only temporary id's, they get replaced when uploaded to
the server
Problem
The data that are used in the application consists of complex objects
(with relations/references to other objects). When i am saving to the
server, i wanted the views to get updated with the new "real" id's.
However, since JavaScript works with objects as references im not able to
do what i want to: $scope.data = newdata This is not overwriting
$scope.data but creates a new object. The old reference to the old data is
still there.
Simplified example
var x = {id: 1, name: "myObject"}
var c = x // c = {id: 1, name: "myObject"}
x = {id: 2, name: "myNewObject"}
// c = {id: 1, name: "myObject"}
As you can see, c is still a reference to the old object. In practice,
this causes that my view isn't updated with new data since it's still
bound to the old data. What i need to is to overwrite the properties of,
in this example, x. I need to do this recursively since my real objects
are complex, however it shouldn't enter any circular references, since
this will probably cause stack overflow. If i am overwriting a with b and
a has properties that b hasn't got, those properties should be removed.
What i need
I need some sort of function that overwrites all properties in a (old
object) with the properties in b (new object). All properties that exists
in a but not in b should be removed.