<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible"comtent="IE-edge">
<meta name="viewport"comtent="width=device-width,initnal-scale=1.0">
<title>计算圆的周长和面积</title>
</head>
<body>
<script>
var r = prompt("请输入圆的半径");
var dec1 = "数据输入格式错误,请重新输入!";
var dec2 = "数据类型符合要求,点击确定计算结果。";
var flag = isNaN(r)?dec1:dec2;
alert(flag);
var R = r * 1;
var C = 2 *Math.PI * R;
var S = Math.PI * (R**2);
document.write("圆的周长:"+C.toFixed(2));
document.write("圆的面积:"+S.toFixed(2));
</script>
</body>
</html>