jqueryImageSwap.js

// Taken from: http://stackoverflow.com/a/9349999

// <img data-other-src="big-zebra.jpg" src="small-zebra.jpg">
// <img data-other-src="big-elephant.jpg" src="small-elephant.jpg">
// <img data-other-src="big-bear.jpg" src="small-bear.jpg">

$(function () {
    $('img').on('mouseenter mouseleave', function () {
        $(this).attr({
            src: $(this).attr('data-other-src'),
            'data-other-src': $(this).attr('src')
        });
    });
});