How to handle an external EventSource as an AngularJS service?

Question

How to handle an external EventSource as an AngularJS service?

I want my controllers to be able to subscribe to an external event source, which I would usually define with:

var source = new EventSource('http://someURL.com/foo');
source.addEventListener('bar', handler, false);

Now let's say that the API I'm working with has only one event proper, but that event gives you a different string depending on what actual event it is. So my handler would look something like:

var handler = function(data) {
   switch(data.cmd) {
       case 'alpha' : doSomething(); break;
       case 'beta' : doSomethingElse(); break;
       case 'cappa' : doAnotherThing(); break;
   }
}

Which is unfortunate, I know, but that's the way it has been implemented. What I want is to be able to expose a service API that makes sense, so in my controllers I would be able to subscribe to each type of event individually, and subscribe once, or repeatedly, as well as unsubscribe.

Does this make sense? Is there a better way to do this that I am missing using the $q API? If not, how would I go about mapping an asynchronous event to an AngularJS service API?

javascript
javascript-events
angularjs

Answer 1

You could register a listener for each message type.

source.addEventListener('alpha', function(e) {
  doSomething();
}, false);

source.addEventListener('beta', function(e) {
  doSomethingElse();
}, false);