I'm working on a Win 8 javascript app that has rss-reader-like capabilities. It should repeatedly check a server for new posts and display a toast, if a new post was found.
My question is, if I should use a background job with a time trigger (that is limited to an interval of 15 minutes) or if a setTimeout / setInterval wouldn't be the better way.
As far as I understand the app lifecycle, my app can be suspended by Windows at any time it is not focussed and Windows decides that timepoint on itself. And if the app is suspended once, neither background jobs will work, nor will the setTimeout / setInterval fire.
If I may, I'd suggest rethinking the notification mechanism here.
If you want to use a toast notification, I'd suggest a push notification. It does require a require a cloud service that does the polling of articles for you and then pushes the notification to subscribing clients; however, it won't tax the battery life of the client nearly as much as a polling trigger.
An issue with toast notifications is that they can be easily missed, so if you want to inform the user of unread articles, you may want to consider a badge notification that will persist on the application tile (like you see on the Mail application). Then at a glance the user will know there are unread articles, versus knowing that only if they happened to see the incoming toast.
Tile and badge notifications can also be updated periodically, which is similar to what you wanted to do with toast, but the mechanism for doing so is much easier. The challenge here though is that periodic notifications aren't generally personalized, that is every user of your app would see the same badge/tile unless you did a bit more work on the server side.