<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 全局方法</h1>
<h2>isNaN() 方法</h2>
<p>"Hello" 是 NaN 吗？</p>
<p id="demo"></p>
<script>
let text = "Hello";
document.getElementById("demo").innerHTML = isNaN(text);
</script>
</body>
</html>