What is the best mobile framework to use to create a simple application for major mobile platforms?

Question

JavaScript

Task: to make an application for mobile operating systems. The functionality is very simple: input field - sending to the server - displaying what the server sent + to this the ability to work in the background (periodic requests to the server), push notifications (this is important) and storing small data on the client side.
I know html and javascript. It is not possible to learn development tools for all operating systems. I want to use a framework, but I don't know which one. Tell me, maybe there is something with javascript that uses the OS interface and is easy to learn.

Answer 1

Here is a description of two frameworks: habrahabr.ru/post/266939 True, taking into account gamedev, but you can get acquainted.
Still very convenient XDK: habrahabr.ru/company/intel/blog/221187