I exaggerated a bit - they have 7656 at the moment (after being 'shut down'). It was the mostly-official place to discuss react, flux, webpack, other tech and libraries in the react ecosystem etc.

In it's peak, there were lots of channels for all the different parts and facets, including geo-oriented channels as well.

Now, its mostly just the dancing shark gif http://i.imgur.com/I2CBRBZ.png