choosing a framework for consuming rest services


I am a Java dev and I have built a restful service with javaEE which I want to consume from web (first) and then mobile.
I am a noob with javascript.

Do you think it is better to avoid any further SS scripting and just build the app with angular or another framework like that or use vaadin to build a server side consumer and the frontend.
Maybe I could use vaadin to only produce a client side consumer?

Do you think time learning JS > time learning vaadin ?

Is the added benefit that I can port easily with touchkit the app to mobile or its not so easy to do this.

thank you