I know it's a pretty general question, but I was wondering what's everyones view on what are some of the best JS API's/Frameworks out there for a new online App? I'm still undecided if whether it will need to be responsive, or if I'll code a native version of the App but for now I'm just interested in learning about what my options are in regards to building an online App with JS.

Access to database functions are very important, and I'm already a fan of Parse.com

Thanks for any help.