[undersheet]

I disagree. Assume you are an average coder, you should have a clue of basic JS:

1 week to learn JS latest language features

1 week to grok node, npm and the power of the JS object

1 week for React, basic stuff not redux

1 more week to dabble around

4 weeks and you should be able to be productive JS with its most important flavors. Tell me any other ecosystem where you are that fast.