JSFiddle - React, Tailwind, and code Playground

JavaScript

var logMsg = "";
var hitsIfChooseToSwitch = 0, hitsIfChooseNotToSwitch = 0;
var SELECTION = 0;
var TEST_RUNS = 1000000;
var i;
for(i = 0; i < TEST_RUNS; i++){
    runTest();
}
log("hitsIfChooseToSwitch: " + hitsIfChooseToSwitch + ", chance is: " 
    + hitsIfChooseToSwitch / TEST_RUNS);
log("hitsIfChooseNotToSwitch: " + hitsIfChooseNotToSwitch + ", chance is: " 
    + hitsIfChooseNotToSwitch / TEST_RUNS);

function runTest(){
    var goats = generateGoats();
    var ruledOut = ruleOutOneGoat(goats, SELECTION);
    var theOtherOne = ruledOut == 0 ? 1 : 0;
    if(theOtherOne == SELECTION){
        hitsIfChooseNotToSwitch++;
    }else{
        hitsIfChooseToSwitch++;
    }
}

function generateGoats(){
    var goats = [0, 1, 2];
    goats.splice(Math.floor(Math.random() * 3),1);
    return goats;
}

function ruleOutOneGoat(goats, selection){
    if(goats[0] == selection){
        return 1;
    }else{
        return 0;
    }
}

function log(msg){
    logMsg += "<pre>"+ msg+"</pre>";
    document.body.innerHTML = logMsg;
}