Is there any plugin which exposes data as JSON and can be visited by AJAX? [closed]

Is there any plugin which exposes data as JSON and can be visited by AJAX? [closed]

I want to use some javascript frameworks (e.g. AngularJs) to write the front end for wordpress.
I'm looking for some plugin which can expose wordpress data (e.g. posts, comments, pages, tags) as JSON, and can be retrieved via AJAX.