JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app
     id="parent"
     ng-controller="parentCtrl">
  <button ng-click="alert()">click me</button>
  
  <div ng-controller="childCtrl">
    
  </div>
</div>

JavaScript

function parentCtrl($scope) {
  $scope.alert = function() {
    for(var i=0; i<subscribers.length; i++) {
      subscribers[i].execute();
    }
  }
  
  var subscribers = [];
  
  $scope.subscribe = function(child) {
    console.log('adding child');
    subscribers.push(child);
  }
}

function childCtrl($scope) {
  this.init = function() {
    $scope.$parent.subscribe(this);
  }
  this.init();
  this.execute = function() {
    console.log('i am child. hear me roar');
  }
}