random-compare-2x.js

const randomPlusRandom = () => Math.random() + Math.random()

const randomTwoTimesRandom = () => 2 * Math.random()

// call `fn()` count-times
// and return the results as an array
const getSequence = (fn, count) => {
  return Array
    // create an array of `count` elements
    .from(Array(count).keys())
    // call `fn()` count-times
    .map(() => fn())
}

const getIntervals = (sequence, nIntervals) => {
  const intervalWidth = 2 / nIntervals

  // intervals
  let intervals = Object.fromEntries(
    Array
      .from(Array(nIntervals).keys())
      .map((el) => [Math.round(el).toString(), 0])
  )

  // loop over `sequence` to categorize each item
  sequence.forEach((item) => {
    // floor of each interval
    const intervalFloor = Math.floor(item / intervalWidth)

    intervals[intervalFloor.toString()] += 1
  })

  // convert to a list
  return Object.entries(intervals)
    .map(([key, value]) =>
      `${(parseInt(key, 10) * intervalWidth)}\t${value}`
    )
    .join('\n')
}

console.log(getIntervals(getSequence(randomPlusRandom, 100000), 20))
console.log(getIntervals(getSequence(randomTwoTimesRandom, 100000), 20))