[integraton]

To provide a counterpoint to many of the responses here, I find that the best way to ramp up quickly in a language is to build a few small things using one or two of the main frameworks or libraries, rather than trying to just learn the language or specifically working only with microframeworks.

There are a lot of benefits that come from using mainstream existing frameworks and libraries from the beginning. You learn conventions pretty quickly, and immediately learn to write idiomatic code for that language. When you use a major framework or library there are typically a lot of blog posts and stackoverflow answers, more so than just for a language itself. When you track down errors you'll end up learning about how the frameworks and libraries work, and thereby learning about how to implement things you wouldn't have considered independently.

As a result, what I'd recommend is coming up with two extremely simple ideas for tools that he'd find useful for himself and implement one each with Ember and React.

Personally, I've been following this approach for many years (I'm currently simultaneously working on three new projects in multiple new-to-me languages like this) and it works extremely well in my experience.