<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 数字</h1>
<p>您可使用全局 JavaScript 函数 isNaN() 来确定某个值是否是数：</p>
<p id="demo"></p>
<script>
var x = 100 / "Apple";
document.getElementById("demo").innerHTML = isNaN(x);
</script>
</body>
</html>