This is a good questions and there is an explanation for you.
First of all note that:
Next you need to note that:
$scope.on(); will be destroyed automatically when the controller loses it representation in view or component (getting destroyed). - You need to destroy
$rootScope.$on() manually.
>> Example of how to destroy $rootScope.on():
//bind event
var registerScope = $rootScope.$on('someEvent', function(event) {
console.log("fired");
});
// auto clean up `$rootScope` listener when controller getting destroy
// listeners will be destroyed by calling the returned function like registerScope();
$scope.$on('$destroy', registerScope);
>>> Since Angular v1.5 we can use component lifecycle to manage init and destroys in a nice way:
var myApp = angular.module('myApp',[]);
myApp.controller('MyCtrl', function ($scope, $rootScope) {
var registerScope = null;
this.$onInit = function () {
//register rootScope event
registerScope = $rootScope.$on('someEvent', function(event) {
console.log("fired");
});
}
this.$onDestroy = function () {
//unregister rootScope event by calling the return function
registerScope();
}
});
This plnkr will show you the different behaviors of $scope.on() and $rootScope.on().
By switching the view in this plunkr the controller will be rebinded to your view. The $rootScope.on(); event is binded every time you switch a view without destroying the event bindings of the view before. In that way the $rootScope.on() listeners will be stacked/multiplied. This will not happen to the $scope.on() bindings because it will be destroyed by switching the view (losing the E2E binding representation in DOM -> controller is destroyed).
The difference between $emit & $broadcast is:
$rootScope.$emit() events only triggers $rootScope.$on() events. $rootScope.$broadcast() will trigger $rootScope.$on() & $scope.on()events (pretty much everthing hear this event).$scope.$emit() will trigger all $scope.$on, all its parents (scopes in parent controllers) and $rootScope.$on().$scope.$broadcast will only trigger $scope and its children (scopes in child controllers).
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