Tried to find some basic information for AngularJS $rootScope.$broadcast
, But the AngularJS documentation doesn't help much. In easy words why do we use this?
Also, inside John Papa's Hot Towel template there is a custom function in the common module named $broadcast
:
function $broadcast() {
return $rootScope.$broadcast.apply($rootScope, arguments);
}
I did not understand what this is doing. So here are couple of basic questions:
1) What does $rootScope.$broadcast
do?
2) What is the difference between $rootScope.$broadcast
and $rootScope.$broadcast.apply
?
$rootScope
basically functions as an event listener and dispatcher.
To answer the question of how it is used, it used in conjunction with rootScope.$on
;
$rootScope.$broadcast("hi");
$rootScope.$on("hi", function(){
//do something
});
However, it is a bad practice to use $rootScope
as your own app's general event service, since you will quickly end up in a situation where every app depends on $rootScope, and you do not know what components are listening to what events.
The best practice is to create a service for each custom event you want to listen to or broadcast.
.service("hiEventService",function($rootScope) {
this.broadcast = function() {$rootScope.$broadcast("hi")}
this.listen = function(callback) {$rootScope.$on("hi",callback)}
})