Deregistering $rootScope function listeners

deregistrationRootScope.js

class MyController {
  constructor($scope, $rootScope) {
    /*
      Every $rootScope.$on returns a deregistration function that remove listerner and avoid duplications
      https://docs.angularjs.org/api/ng/type/$rootScope.Scope#$on
    */
    const deregisterDropdownOpenEvent = $rootScope.$on('DropdownOpened', () => console.log('dispatch event'))
    
    /* Deregister function on scope $destroy event (when user leave the page, for example) */
    $scope.$on('$destroy', () => deregisterDropdownOpenEvent())
  }
}