Bangle.js 2: How do I use it as delivered? Is there any user documentation?

The setInterval function doesn't need to be anonymous:

function doChime() { ... }
let chime = setInterval(doChime, 60 * 1000);

The interval is in milliseconds, so the example is 1 minute intervals. See http://www.espruino.com/Reference#l__glo­bal_setInterval