squre,rect and circle perameter in js.html

<html>

<head>
	<script>

		function chek_value() {
			m = parseInt(prompt("Enter value of m  "));
			n = parseInt(prompt("Enter value of n "));
			var area;
			area = m * n;
			per = 2 * (m + n);
			return per;
		}
		function chek_value2() {
			var pi = 3.14;
			var rad = parseInt(prompt("Enter value of radius "));
			var area;
			area = pi * rad * rad;
			per = 2 * pi * rad;
			return per;
		}

		function chek_value3() {
			s = parseInt(prompt("Enter value of s "));
			var area;
			area = s * s;
			per = 4 * s;
			return per;
		}

	</script>
</head>

<body>
	<script>
		var arr;
		arr = chek_value();
		document.write("perameter of rectangle is=" + arr + "<br>");
		var arr2;
		arr2 = chek_value2();
		document.write("perameter of circle is=" + arr2 + "<br>");
		var arr3;
		arr3 = chek_value3();
		document.write("perameter of squre is=" + arr3 + "<br>");

	</script>
</body>

</html>