代码示例:(标识:eg_js_math_pi)
<!DOCTYPE html>
<html>
<body>

<h1>JavaScript Math.PI</h1>

<p>Math.PI 返回圆周长与直径的比率:</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML = Math.PI;
</script>

</body>
</html>
运行结果: