实现jquery的after
<div>
<input type=radio id="a"/>
<input type=radio id="b"/>
</div>
$("#a").after("a");
$("#b").after("b");
<div>
<input type=radio id="a"/>
<input type=radio id="b"/>
</div>
<script type="text/javascript">
var node=document.createTextNode("a"),input=document.getElementById('a'),div=input.parentNode;
div.appendChild(node)
div.insertBefore(input,node)
node=document.createTextNode("b")
input=document.getElementById('b')
div.appendChild(node)
div.insertBefore(input,node)
</script>
var a=document.createTextNode("a")
var b=document.createTextNode("b")
document.getElementById("a").parentNode.insertBefore(a, document.getElementById("a").nextSibling);
document.getElementById("b").parentNode.insertBefore(b, document.getElementById("b").nextSibling);