Simple implementation of Elo rating system in typescript

elo.ts

// https://en.wikipedia.org/wiki/Elo_rating_system

const K = 32

export enum EloStatus {
  LOOSE = 0,
  DRAW = 0.5,
  WIN = 1
}

const delta = (score: number, opponent: number, status: EloStatus) => {
  const probability = 1 / (1 + Math.pow(10, (opponent - score) / 400))
  return Math.round(K * (status - probability))
}

export default (score: number, opponent: number, status: EloStatus) => {
  return score + delta(score, opponent, status)
}