js获取某id下面的div元素个数并判断输出

<style>
.fl{float:left;}
.fr{float:right;}
</style>
<div class="box03" id="abc">
<dl>1</dl>
<dl>1</dl>
<dl>1</dl>
</div>
<script type="text/javascript">
var objName=document.getElementById("abc").getElementsByTagName("dl");
for (i=0;i<objName.length;i++) {
(i%2==0)?(objName[i].className = "fl"):(objName[i].className = "fr");
}
</script>