JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.7/angular.min.js"></script>
<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
<body ng-app="MyApp">
    <div ng-controller="parentCtrl">
        <p>{{user.name}}</p>
        <div ng-controller="childCtrl">
            <p>{{user.name}}</p>
        </div>
    </div>
</body>

JavaScript

var app = angular.module("MyApp", []);


app.service('authenticationSrv', function () {
    var user = 'anonymous';
    return {
        getUser: function () {
            return user;
        },
        setUser: function (value) {
            user = value;
        }
    };
});

app.controller("parentCtrl", function ($scope, authenticationSrv) {
    $scope.user = {};
    $scope.user.name = authenticationSrv.getUser();
});

app.controller("childCtrl", function ($scope, authenticationSrv) {
    authenticationSrv.setUser('my name'); // I need this function to also update the scope of the parent
    $scope.user.name = authenticationSrv.getUser();
});