Exams - Bulls and Cows (on JavaScript)

/* All we love the “Bulls and Cows” game (http://en.wikipedia.org/wiki/Bulls_and_cows).
 Given a 4-digit secret number and a 4-digit guess number we say that we have b bulls and c cows when we have
 b matching digits on their right positions (bulls) and c matching digits on different positions (cows).
 Given the secret number and the number of bulls and cows your task is to write a program to find
 all matching guess numbers in increasing order.
 The secret number will always consist of exactly 4 digits, each in the range [1…9]!
 The input will consist of exactly 3 lines. At the first line there the secret number will be given.
 At the second line the number of bulls b will be given. At the third line the number of cows c will be given.
 The output should consist of a single line holding all matched guess numbers, given in increasing order,
 separated by single space. */

"use strict";

function solve(args) {
    var secretStr = args[0];
    var bulls = parseInt(args[1]);
    var cows = parseInt(args[2]);

    Array.prototype.contains = function (checkElement) {
        for (var index in this) {
            if (this.hasOwnProperty(index)) {
                if (this[index] === checkElement) {
                    return true;
                }
            }
        }
        return false;
    };

    var matchedNumbers = [];
    var num, secretNumber, guessNumber;
    for (num = 1111; num < 10000; num += 1) {
        guessNumber = num.toString().split('');
        if (!guessNumber.contains('0')) {
            secretNumber = secretStr.split('');
            var countBulls = getBullsDigits();
            var countCows = getCowsDigits();
            if (countBulls == bulls && countCows == cows) {
                matchedNumbers.push(num);
            }
        }
    }

    if (matchedNumbers.length) {
        console.log(matchedNumbers.join(' '));
    } else {
        console.log('No');
    }

    function getBullsDigits() {
        var countBulls = 0;
        for (var i = 0; i < 4; i += 1) {
            if (guessNumber[i] == secretNumber[i]) {
                guessNumber[i] = '-';
                secretNumber[i] = '*';
                countBulls += 1;
            }
        }

        return countBulls;
    }

    function getCowsDigits() {
        var countCows = 0;
        if (countBulls < 3) {
            for (var i = 0; i < 4; i += 1) {
                for (var j = 0; j < 4; j += 1) {
                    if (guessNumber[j] == secretNumber[i]) {
                        guessNumber[j] = '-';
                        secretNumber[i] = '*';
                        countCows += 1;
                    }
                }
            }
        }

        return countCows;
    }
}

solve(['2228', '2', '1']);
solve(['1234', '3', '0']);
solve(['1234', '3', '1']);