JavaScript event delegation example

gistfile1.js

    window.onload = function() {
        if(document.body.addEventListener) {
            document.body.addEventListener('mouseover', onMouseOverHandler, false);
            document.body.addEventListener('mouseout', onMouseOutHandler, false);
        } else {
            document.body.attachEvent('onmouseover', onMouseOverHandler);
            document.body.attachEvent('onmouseout', onMouseOutHandler);
        }

        function switchImage(e, o) {
            var srcstr = '.png', dststr = '-sel.png';
            if(!o) dststr = [srcstr, srcstr = dststr][0];
            var myE = e.children[0];
            myE.setAttribute('src', myE.getAttribute('src').replace(srcstr, dststr));
        }

        function onMouseOverHandler(e) {
            e = e || window.event;
            var target = e.target || e.srcElement;

            console.log(target);

            if (target.className.match(/menu-item-link/)) {
                switchImage(target, 1);
            }
        }

        function onMouseOutHandler(e) {
            e = e || window.event;
            var target = e.target || e.srcElement;

            if (target.className.match(/menu-item-link/)) {
                switchImage(target, 0);
            }
        }
    }

HTML code missing. This is just to get an idea (review in case of c&p).