สอบถามการสร้าง document.createElement("input") แล้วต้องการใส่ class

<SCRIPT language="javascript" type="text/javascript">
var n = 1;
var w = 1; 
function mknormal(){
	w = 1;
	n = 1;
	document.getElementById("tx").innerHTML= '<input name="file1" type="file" /><br />';
	//document.F1.action = "";
}

function plus(){
	if (w==1) { plusnormal(); }
	if (w==2 && n<5){ plusremote(); }
}

function plusremote() {
	n = n+1;
	var main = document.getElementById("tx");
	document.getElementById("dasminus").style.visibility='visible';
	document.getElementById("dasminus").style.fontSize='20px';
	var newnode = document.createElement("input");
	newnode.type="text";
	newnode.name="link";
	
	main.appendChild(newnode);
	main.appendChild(document.createElement("br"));
}

function plusnormal() {
	n = n+1;
	document.getElementById("dasminus").style.visibility='visible';
	document.getElementById("dasminus").style.fontSize='20px';
	var main = document.getElementById("tx");
	var newnode = document.createElement("input");
	newnode.type="file";
	newnode.name="file"+n;
	
	main.appendChild(newnode);
	main.appendChild(document.createElement("br"));
}

function minus() {
	if (n>1) {
		n = n-1;
		var main = document.getElementById("tx");
		main.removeChild(main.lastChild);
		main.removeChild(main.lastChild);
	}
	if (n==1){
		document.getElementById("dasminus").style.visibility='hidden';
		document.getElementById("dasminus").style.fontSize='1px';
	}
}
</SCRIPT>