Basic statistics on a random number generator

random_number_statistics.js

const MIN_INT = 1;
const MAX_INT = 5;
const ROUNDS = 1000;
const FLOATING_ACCURACY = 2;

function getRandomInt(min = MIN_INT, max = MAX_INT){
  min = Math.ceil(min);
  max = Math.floor(max);
  return Math.floor(Math.random() * (max - min + 1)) + min; 
}

function roundToDecimalPoints(number, decimalPoints = FLOATING_ACCURACY) {
  const accuracyInTens = Math.pow(10, decimalPoints);
  return Math.round(accuracyInTens * number) / accuracyInTens;
}

const results = {};
for (let i = 0; i < ROUNDS; i++) {
  const randomNumber = getRandomInt();
  if (!results[randomNumber]) results[randomNumber] = {value: 0};
  results[randomNumber].value++;
}

const expected = roundToDecimalPoints(ROUNDS / (MAX_INT - MIN_INT + 1));
const pct_expected = roundToDecimalPoints(100 * expected / ROUNDS);
for (const key of Object.keys(results)) {
  const pct = roundToDecimalPoints(100 * results[key].value / ROUNDS);

  results[key].expected = expected;
  results[key].diff = results[key].value - expected;
  results[key].pct = pct;
  results[key].pct_expected = pct_expected;
  results[key].pct_diff = roundToDecimalPoints(pct - pct_expected);
}

console.table(results);