Stuck with mootools script. Image autochange

Stuck with mootools script. Image autochange

<div id="contentimage">
<img src="1.jpg" class="activeimage" />
<img src="2.jpg" style="opacity: 0;" />
<img src="3.jpg" class="last" style="opacity: 0;" />
</div>
<script>
window.addEvent('domready', function() {
var fx = function() {
var activeimage = $$('img.activeimage');
if(!activeimage.hasClass('last')) {
var next = activeimage.getNext('img');
activeimage.toggleClass('activeimage');
next.toggleClass('activeimage');
activeimage.morph({'opacity':'0'});
next.morph({'opacity':'1'});
} else {
var next = $('contentimage').getFirst('img');
activeimage.toggleClass('activeimage');
next.toggleClass('activeimage');
activeimage.morph({'opacity':'0'});
next.morph({'opacity':'1'});
}
}
fx.periodical(3000);
});
</script>
I just can't understand why this :
if(!activeimage.hasClass('last'))
always returns false ? I tried to check it with "alert", and it was all
good, but when it comes to this line - it goes not like I expected.