It supports directly connecting to BLE adaptors for Windows versions <8.1, or in the case of 8.1 and later it'll use the Windows APIs to go via the drivers... So even though Web Bluetooth isn't there yet you'll still be fine.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
And... A downloadable Web IDE for Windows is now here: http://www.espruino.com/Web+IDE
It supports directly connecting to BLE adaptors for Windows versions <8.1, or in the case of 8.1 and later it'll use the Windows APIs to go via the drivers... So even though Web Bluetooth isn't there yet you'll still be fine.