如何在if语句之后交换HTML中的相邻图像

Question

如果我点击空白单元格旁边的图片（上方，左侧，右侧或下方），则需要交换我单击的单元格的位置和空白单元格。

我的桌子是6x6，我认为我有正确的方法，但它没有交换......

空白单元格称为blank.jpg，其他所有单元格均为01.jpg - 35.jpg

function move(n)
{
    var clickedImage = document.images[n].src;
    var leftImage    = document.images[n-01].src;
    var rightImage   = document.images[n+01].src;
    var upImage      = document.images[n-06].src;
    var downImage    = document.images[n+06].src;

    var leftNum  = leftImage.charAt(leftImage.length-5);
    var rightNum = rightImage.charAt(rightImage.length-5);
    var upNum    = upImage.charAt(upImage.length-5);
    var downNum  = downImage.charAt(downImage.length-5);

    if (isNan(leftNum))
    {
        a            = clickedImage
        b            = leftImage
        clickedImage = b
        leftImage    = a
    }
    else if (isNan(rightNum))
    {
        a            = clickedImage
        b            = rightImage
        clickedImage = b
        rightImage   = a
    }
    else if (isNan(upNum))
    {
        a            = clickedImage
        b            = upImage
        clickedImage = b
        upImage      = a
    }
    else if (isNan(downNum))
    {
        a            = clickedImage;
        b            = downImage;
        clickedImage = b;
        downImage    = a;
    }
}