is it correct?

[vinnitu]

trafficstars

https://github.com/node-webrtc/node-webrtc-examples/blob/f1d7b9a8483fac1a5b2b48da0dde3b2366b5225f/lib/common/pitchdetector.js#L64

maybe you mean?

function averageDifference(xs) {
  return pairs(xs).reduce((y, [x1, x2]) => (x2 - x1) + y, 0) (xs.length - 1);
}