dice.js

/*

Monte Carlo Simulation for 🎲 🎲
Example output for 1,000,000 simulations

 2: ⬜⬜⬜
 3: ⬜⬜⬜⬜⬜
 4: ⬜⬜⬜⬜⬜⬜⬜
 5: ⬜⬜⬜⬜⬜⬜⬜⬜⬜
 6: ⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜
 7: ⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜
 8: ⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜⬜
 9: ⬜⬜⬜⬜⬜⬜⬜⬜⬜
10: ⬜⬜⬜⬜⬜⬜⬜
11: ⬜⬜⬜⬜⬜
12: ⬜⬜⬜

*/

const { range, curry, inc, times, compose, toPairs } = require("ramda");
const { random, floor, ceil, min, max } = Math;
const { assign, values, keys } = Object;

const generateRandom = (minOutput, maxOutput) => 
  floor(random() * (maxOutput - minOutput + 1) + minOutput);

const initHistogram = (minOutput, maxOutput) =>
  range(minOutput, maxOutput + 1).reduce(initHistogramEntry, {});

const initHistogramEntry = (histogram, possibleOutput) =>
  assign(histogram, { [possibleOutput]: 0 });

const computeResult = curry((histogram, result) =>
  assign(histogram, { [result]: inc(histogram[result]) }));

const runRound = (histogram, generator) =>
  compose(computeResult(histogram), generator);

const simulate = (minOutput, maxOutput, numOfRuns, generator) => {
  const histogram = initHistogram(minOutput, maxOutput);
  times(runRound(histogram, generator), numOfRuns);
  return histogram;
}

const plotRow = curry((bucketSize, entry) => {
  const bucket = ceil(entry[1] / bucketSize);
  const formattedVal = Array(bucket).fill("⬜", 0).join("");
  const formattedKey = entry[0].padStart(2, " ");
  return [formattedKey, formattedVal].join(": ");
});

const plot = (histogram) => {
  const frequencies = values(histogram);
  const leastLikely = min(...frequencies);
  const mostLikely = max(...frequencies);
  const bucketSize = ceil((mostLikely - leastLikely) / frequencies.length);
  return toPairs(histogram).map(plotRow(bucketSize)).join("\n");
}

// run dices example

const minOutput = 2;
const maxOutput = 12;
const numOfRuns = 100000;
const rollDices = () => generateRandom(1, 6) + generateRandom(1, 6);

const histogram = simulate(minOutput, maxOutput, numOfRuns, rollDices);

console.log(plot(histogram));