The immediate problem is that a attrName property isn't part of jQuery's event's object...you need to use e.originalEvent.attrName. Here's an example of it working:

var first_img = $(body).find(div).first();



first_img.on(DOMAttrModified, function (e) {

    if (e.originalEvent.attrName === class) {

        console.log(##DOMAttrModified, class changed);

        if ($(this).hasClass(current-image)) {

            console.log(##Element has 'current-image' class, changing);

            $(this).removeClass().addClass(previous-image);

        }

    }

});



setTimeout(function () {

    first_img.addClass(current-image);

}, 1000);

DEMO: http://jsfiddle.net/R5rTy/1/

The setTimeout is to simulate the event randomly happening.

Apparently, the DOMAttrModified event is not supported in all browsers - http://help.dottoro.com/ljfvvdnm.php#additionalEvents

UPDATE:

Using the newer MutationObserver, the following shows the use of both ideas:

var firstImg, observerConfig, firstImgObserver;



firstImg = $(body).find(div).first();

observerConfig = {

    attributes: true,

    childList: true,

    characterData: true

};

firstImgObserver = new MutationObserver(function (mutations) {

    mutations.forEach(function (mutation) {

        var newVal = $(mutation.target).prop(mutation.attributeName);

        if (mutation.attributeName === class) {

            console.log(MutationObserver class changed to, newVal);

        } else if (mutation.attributeName === id) {

            console.log(MutationObserver id changed to, newVal);

        }

    });

});



firstImgObserver.observe(firstImg[0], observerConfig);

// later, you can stop observing

//observer.disconnect();



firstImg.on(DOMAttrModified, function (e) {

    var newVal = $(this).prop(e.originalEvent.attrName);

    console.log(DOMAttrModified, e.originalEvent.attrName, changed to, newVal);

});



setTimeout(function () {

    firstImg.addClass(previous-image).addClass(fdsa);

}, 1000);

DEMO: http://jsfiddle.net/ybGCF/

Reference:

• https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver