A JavaScript code to test the Monty Hall Problem.

MontyHallProblem.js

var myBet = Math.floor(Math.random() * 3) + 1;
var acceptChangeInitialBet = Math.floor(Math.random() * 2) + 1;

function game(initialBet, changeInitialBet) {
	var portsAndPrizes = [];
	var carPort = Math.floor(Math.random() * 3) + 1;
	var newBet;
	var discardedDoor;
	var finalGoatDoor;
	var finalBet;

	finalBet = initialBet;
	portsAndPrizes[carPort] = "car";

	for(var i = 1; i < 4; i++) {
		if(i != carPort)
			portsAndPrizes[i] = "goat";
	}

	function discardingAPossibility() {
		for(var i = 1; i < 4; i++) {
			if(i != carPort && i != initialBet) {
				discardedDoor = i;
				console.log(`Showing to you that behind door #${discardedDoor} we have a goat!`);
				break;
			}
		}
	}

	function printPortsAndPrizes() {
		for(var i = 1; i < 4; i++) {
			console.log(`Behind door #${i} we have: ${portsAndPrizes[i]}`);
		}
	}

	function changeInitialBet(initialBet) {
		for(var i = 1; i < 4; i++) {
			if(i != initialBet && i != discardedDoor) {
				newBet = i;
				finalBet = newBet;
				console.log(`Your new bet is in the door #${newBet}, good luck!`);
				break;
			}
		}
	}

        console.log(`Your initial bet is in the port #${initialBet}`);
	//printPortsAndPrizes();
	discardingAPossibility();
	console.log("Do you want change your inicial bet?");
	console.log(`Answer: ${acceptChangeInitialBet}`);
	if(acceptChangeInitialBet == 1)
		changeInitialBet(initialBet);


	if(finalBet == carPort)
		console.log("Congratulations, you win a new brand car!");
	else
		console.log("Congratulations, you win an old smelly goat!");
}

game(myBet, acceptChangeInitialBet);


/* 
Console log:

"Your initial bet is in the port #1"
"Showing to you that behind door #2 we have a goat!"
"Do you want change your inicial bet?"
"Answer: 2"
"Congratulations, you win an old smelly goat!"
*/

Recently appears a lot of entries in the Medium about Monty Hall Problem, some impassioned by a Brooklyn Nine-Nine episode.

This code in JavaScript demonstrate how the problem work:

Imagine that you were invited to a TV game where you will try win a car.
To do it you have to choose a door of three doors.
The presenter of the game, after you choose, open a door and show to you a goat, and offers to you a chance to change your initial bet.

At this point, changing your mind and choosing another door, your changes of win a new car will increase or decrease?

Will increase!
Your expectative of win will be 2/3 not 1/3.

Run this code sometimes and you will see this, 66% of incensements when you change the initial bet!