expert-m / react-split-testing

function getRandom(seed) {

  let newSeed = 0

  for (let i = 0; i < seed.length; i++) {

    newSeed += seed.charCodeAt(i) * Math.pow(10, i)

  }

  const x = Math.sin(newSeed) * 10000

  return x - Math.floor(x)

}

export default function weightedRandom(weights, randomSeed) { // randomSeed must be a string

  if (!randomSeed) {

    return -1

  }

  let totalWeight = 0

  for (let i = 0; i < weights.length; i++) {

    totalWeight += weights[i]

  }

  let random = getRandom(randomSeed) * totalWeight

  for (let i = 0; i < weights.length; i++) {

    if (random < weights[i]) {

      return i

    }

    random -= weights[i]

  }

  return -1

}