js动态添加id

<script type="text/javascript">
function add_id(){
var dlall=document.getElementsByTagName('div');
for(i=0;i<dlall.length;i++){
dlall[i].id='id_'+i;
}
}
window.onload=add_id;
</script>
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>