/**
 * Prohodi v danem elementu tridy
 * 
 * @param {String} el element na kterem provest vymenu 
 * @param {String} class_1 Prvni trida
 * @param {String} class_2 Druha trida
 */
function swap_classes(el, class_1, class_2)
{
    
    if (el)
    {
        if (-1 != el.className.search(class_1))
        {
            el.className = el.className.replace(class_1, class_2)
        } 
        else
        if (-1 != el.className.search(class_2))
        {
            el.className = el.className.replace(class_2, class_1)
        } 
    }
}

function hover(el)
{
    swap_classes(el, 'hover', 'noHover');
}