montecarlo.js

var Lazy = require('lazy.js');

function isHeads(x) { return x >= 0.5; }
function isTails(x) { return x  < 0.5; }

function toss(n) {
  var successes = Lazy.generate(function() { return Math.random(); })
    .take(n)
    .filter(isHeads)
    .size();

  return successes / n;
}

console.log(
  Lazy.generate(function () { return toss(45) }).take(100).toArray()
);