JavaScript输入圆的半径计算周长及面积
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>计算圆的周长面积</title>
</head>
<script>
var r = window.prompt("请输入圆的半径"," ");
var π=3.14;
c=2*π*r;
s=π*r*r;
document.write('圆的周长:'+c+'<br>'+'圆的面积:'+s);
</script>
<body>
</body>
</html>