How to make simple javascript calculator

	<script type="text/javascript">
		var num1,num2;

		num1=prompt("Enter a num");
		num2=prompt("Enter a num");

		num1=parseInt(num1,10);
		num2=parseInt(num2,10);

		var sum,sub,div,mul;

		sum=num1+num2;
		document.write(num1+"+"+num2+"="+sum + "<br/>");

		sub=num1-num2;
		document.write(num1+"-"+num2+"="+sub+"<br/>");

		div=num1/num2;
		document.write(num1+"/"+num2+"="+div+"<br/>");

		mul=num1*num2;
		document.write(num1+"*"+num2+"="+mul + "<br/>");         

	</script>