JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app="app">
    <div ng-controller="OneController">
    <h2>OneController</h2>
    <button ng-click="buttonClick()">
        buttonClick on current scope
    </button>
    <button ng-click="buttonClickOnTwoController()">
        buttonClick on TwoController's scope
    </button>
</div>

<div ng-controller="TwoController">
    <h2>TwoController</h2>
    <button ng-click="buttonClick()">
        buttonClick on current scope
    </button>
    <button ng-click="buttonClickOnOneController()">
        buttonClick on OneController's scope
    </button>
</div>
</div>

JavaScript

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

app.run(function ($rootScope) {
    $rootScope.$on('scope.stored', function (event, data) {
        alert("scope.stored", data);
    });
});
app.controller('OneController', function ($scope, Scopes) {

    Scopes.store('OneController', $scope);

    $scope.variable1 = "One";

    $scope.buttonClick = function () {
        console.log("OneController");
        alert("OneController::variable1", Scopes.get('OneController').variable1);
        alert("TwoController::variable1", Scopes.get('TwoController').variable1);
        alert("$scope::variable1", $scope.variable1);
    };

    $scope.buttonClickOnTwoController = function () {
        Scopes.get('TwoController').buttonClick();
    };
});
app.controller('TwoController', function ($scope, Scopes) {

    Scopes.store('TwoController', $scope);

    $scope.variable1 = "Two";

    $scope.buttonClick = function () {
        console.log("TwoController");
        console.log("OneController::variable1", Scopes.get('OneController').variable1);
        console.log("TwoController::variable1", Scopes.get('TwoController').variable1);
        console.log("$scope::variable1", $scope.variable1);
    };

    $scope.buttonClickOnOneController = function () {
        Scopes.get('OneController').buttonClick();
    };
});
app.factory('Scopes', function ($rootScope) {
    var mem = {};

    return {
        store: function (key, value) {
            $rootScope.$emit('scope.stored', key);
            mem[key] = value;
        },
        get: function (key) {
            return mem[key];
        }
    };
});