DebugMessages = false;

function randomInt(maxValue){
  return Math.floor(Math.random() * maxValue);
}

function HideAutoInCells(cells){
  var AutoCellNum = randomInt(3);
  
  for (var i = 0; i < 3; i++)
    cells[i] = (i == AutoCellNum);
  
  if (DebugMessages)
    WScript.Echo('cells: ' + cells.toString());
}

function MakeFirstChoice(){
  return randomInt(3);
}

function GetCellToOpen(firstChoice, cells){
  for (var i = 0; i < 3; i++)
    if ((!cells[i]) && (i != firstChoice)) 
      return i;
}

function MakeSecondChoice(firstChoice, cells){

  var openedCell = GetCellToOpen(firstChoice, cells);
  if (DebugMessages)
    WScript.Echo('opened cell: ' + openedCell);
  
  for (var i = 0; i < 3; i++)
    if ((i != firstChoice) && (i != openedCell))
      return i;
}

IterationsCount = 1000;

var cells = new Array(3);
var firstChoice;
var secondChoice;
var firstChoiceHitsCount = 0;
var secondChoiceHitsCount = 0;

for (var i = 0; i < IterationsCount; i++) {
  HideAutoInCells(cells);

  firstChoice = MakeFirstChoice();
  if (DebugMessages)
    WScript.Echo('first choice: ' + firstChoice);
  if (cells[firstChoice]) 
    firstChoiceHitsCount++;

  secondChoice = MakeSecondChoice(firstChoice, cells);
  if (DebugMessages)
    WScript.Echo('second choice: ' + secondChoice);
  if (cells[secondChoice]) 
    secondChoiceHitsCount++;
}

WScript.Echo('result: ' + firstChoiceHitsCount + ' vs ' + secondChoiceHitsCount);

result: 309 vs 691
result: 364 vs 636
result: 333 vs 667
result: 341 vs 659