by using Javascript, how to list all the attributes of a html element?

thanks

<script type="text/javascript" >

el=document.getElementById(ID);
for(i=0;i<el.attributes.length;i++){
	 document.write(el.attributes[i].nodeName);
	 document.write(' = ');
	 document.write(el.attributes[i].nodeValue);
	 document.write(' <br>');	
}
</script>