I'm curious and couldn't find the info from a quick search of the repo, how much flash space does the JS virtual machine take up? And how much space is left to include libraries you may need?

Between the Arduino runtime, wifi library, mqtt library, libraries for talking to peripherals, and my C++ application code I'm already getting pretty close to the 512KiB limit for an ESP8266-based thermostat I've been working on. Hard to imagine JS being small enough to fit on that, but perhaps it's designed for embedded chips with a bit more flash space available