Bulls and cows game Ruby vs JavaScript. (Credit: http://rosettacode.org/wiki/Bulls_and_cows)

bulls_and_cows.rb

size = 4
secret = [*'1' .. '9'].sample(size)
guess = nil
 
i=0
loop do
  i+=1
  loop do
    print "Guess #{i}: "
    guess = gets.chomp.chars
    exit if guess.empty?
 
    break if guess.size == size and 
             guess.all? { |x| ('1'..'9').include? x } and
             guess.uniq.size == size
 
    puts "Problem, try again. You need to enter #{size} unique digits from 1 to 9"
  end
 
  if guess == secret
    puts "Congratulations you guessed correctly in #{i} attempts"
    break
  end
 
  bulls = cows = 0
  size.times do |j|
    if guess[j] == secret[j]
      bulls += 1
    elsif secret.include? guess[j]
      cows += 1
    end
  end
 
  puts "Bulls: #{bulls}; Cows: #{cows}"
end

bullsAndCows.js

#!/usr/bin/env js
 
function main() {
    var len = 4;
    playBullsAndCows(len);
}
 
function playBullsAndCows(len) {
    var num = pickNum(len);
    // print('The secret number is:\n  ' + num.join('\n  '));
    showInstructions(len);
    var nGuesses = 0;
    while (true) {
        nGuesses++;
        var guess = getGuess(nGuesses, len);
        var census = countBovine(num, guess);
        showScore(census.bulls, census.cows);
        if (census.bulls == len) {
            showFinalResult(nGuesses);
            return;
        }
    }
}
 
function showScore(nBulls, nCows) {
    print('    Bulls: ' + nBulls + ', cows: ' + nCows);
}
 
function showFinalResult(guesses) {
    print('You win!!! Guesses needed: ' + guesses);
}
 
function countBovine(num, guess) {
    var count = {bulls:0, cows:0};
    var g = guess.join('');
    for (var i = 0; i < num.length; i++) {
        var digPresent = g.search(num[i]) != -1;
        if (num[i] == guess[i]) count.bulls++;
        else if (digPresent) count.cows++;
    }
    return count;
}
 
function getGuess(nGuesses, len) {
    while (true) {
        putstr('Your guess #' + nGuesses + ': ');
        var guess = readline();
        guess = String(parseInt(guess)).split('');
        if (guess.length != len) {
            print('  You must enter a ' + len + ' digit number.');
            continue;
        }
        if (hasDups(guess)) {
            print('  No digits can be duplicated.');
            continue;
        }    
        return guess;
    }
}
 
function hasDups(ary) {
    var t = ary.concat().sort();
    for (var i = 1; i < t.length; i++) {
        if (t[i] == t[i-1]) return true;
    }
    return false;
}
 
function showInstructions(len) {
    print();
    print('Bulls and Cows Game');
    print('-------------------');
    print('  You must guess the ' + len + ' digit number I am thinking of.');
    print('  The number is composed of the digits 1-9.');
    print('  No digit appears more than once.');
    print('  After each of your guesses, I will tell you:');
    print('    The number of bulls (digits in right place)');
    print('    The number of cows (correct digits, but in the wrong place)');
    print();
}
 
function pickNum(len) {
    var nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];
    nums.sort(function(){return Math.random() - 0.5});
    return nums.slice(0, len);
}
 
main();