javascript DOM操作之插入节点

<script type="text/javascript">
window.onload = function aa()
{
var oDiv = document.createElement('div');
var oText = document.createTextNode('hello');
oDiv.appendChild(oText);
 
var id = document.getElementById('a1');
if(id.nextSibling.nodeType==1)
{
nextId = id.nextSibling;
}
else
{
nextId = id.nextSibling.nextSibling;
}
nextId.appendChild(oDiv);
}
</script>

<div id="a1">1</div>
<div id="a2">2</div>
<div id="a3">3</div>