Based on what metric? A Facebook team talking about a Facebook framework and a HN thread filled with React enthusiasts? I am not bashing any of it, but to suggest critical mass is a bit immature.

Yeah, I have yet to meet a react developer in person. Maybe the definition of 'critical mass' is just enough fans to have commentors posting about it 24 hours a day. I would say rust has reached critical mass if react has.

The community enthusiasm and features add up to the critical mass necessary to push me into giving it a good look... also, I wanted to say "critical mass" in connection with "React" ;)