<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 数字</h1>
<h2>valueOf() 方法</h2>
<p>valueOf() 返回数字的原始值：</p>
<p id="demo"></p>
<script>
let num = 15;
let n = num.valueOf();
document.getElementById("demo").innerHTML = n;
</script>
</body>
</html>