Euclidean distance formula

euclideanDistance.js

function euclideanDistance (user1, user2) {
  const n = _.size(user1.reviews)
  let coefficient = 0

  if (n === 0) {
    return n
  }

  for (let i = 0; i < n; i++) {
    coefficient += Math.pow(user1.reviews[i].rating - user2.reviews[i].rating, 2)
  }

  return 1 / (1 + Math.sqrt(coefficient))
}