Did you do what it says right at the start of https://googlechrome.github.io/samples/web-bluetooth/scan.html?namePrefix=Bangle&allAdvertisements=true ?
You must be using Chrome 79+ with the chrome://flags/#enable-experimental-web-platform-features flag enabled.
@Gordon started
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.
Did you do what it says right at the start of https://googlechrome.github.io/samples/web-bluetooth/scan.html?namePrefix=Bangle&allAdvertisements=true ?