function randomBanner(numberOfBanners) {
    var bannerURL = $("#bannerImage1").attr("src");
    var bannerImages = Array(numberOfBanners);
    myRegEx = new RegExp("(\\d+)");
    for (i = 0; i < numberOfBanners; i++) {
        bannerImages[i] = bannerURL.replace(myRegEx, padIntegerLeadingZeros(i + 1, myRegEx.exec(bannerURL)[1].length));
    }

    randomIdx = Math.floor(Math.random() * numberOfBanners);

    return bannerImages[randomIdx];
}

function padIntegerLeadingZeros(integer, totalLength)
{
    var intAsString = integer.toString();
    
    while (intAsString.length < totalLength) {
        intAsString = "0" + intAsString;
    }
    
    return intAsString;
}