<div id="change">
<div name="bg" class="1">
1111
</div>
<div name="bg" class="1">
1111
</div>
<div name="bg" class="1">
1111
</div>
<div name="bg" class="1">
1111
<div class="hh">
</div>
<div class="hh">
</div>
</div>
</div>
<script type="text/javascript">
$("div[name='bg']:even").attr("class", "2222");
<div name="bg" class="1">
1111
</div>
<div name="bg" class="1">
1111
</div>
<div name="bg" class="1">
1111
</div>
<div name="bg" class="1">
1111
<div class="hh">
</div>
<div class="hh">
</div>
</div>
</div>
<script type="text/javascript">
$("div[name='bg']:even").attr("class", "2222");
</script>
注:name=bg 的div可以循环