Modification free selection of random weighted element

weightedRandom.js

  const d = {
    share: 5,
    promote: 6,
    engage: 11,
    discover: 1
  }

  const total = _(d).values().sum();

  const buckets = _(d)
    .mapValues(v => v / total)
    .toPairs()
    .value();

  function randomBucket(buckets, r){
    const [name, perc] = _.head(buckets);
    if (r - perc < 0) return name;

    return randomBucket(_.tail(buckets), r - perc)
  }



  console.log(total);
  console.log(d);
  console.log(buckets);
  console.log(randomBucket(buckets, Math.random()))