Use web-sockets .. So, that the client doesn't needs to worry about the changes in data at server end. The server will auto-push the changes to client whenever their is any change.
Meteor has such a world class implementation of same functionality out of the box.
There are number web-socket modules for Angular . github.com/AngularClass/angular-websocket . On server-end web-sockets are supported by almost all languages natively.