Espruino runs JavaScript on microcontrollers

A JavaScript interpreter for embedded devices. Write firmware in JS, upload over USB or Bluetooth, iterate without compilation cycles.

The trade-off: slower than C, but dramatically faster development. Good fit for prototyping, sensor projects, and situations where ease of modification beats raw performance.

Official boards (Puck.js, Bangle.js) include BLE and sensors out of the box.

See also: simcap