<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 数字</h1>
<h2>toPrecision() 方法</h2>
<p>toPrecision() 将数字格式化为指定长度：</p>
<p id="demo"></p>
<script>
let num = 13.3714;
document.getElementById("demo").innerHTML = num.toPrecision(2);
</script>
</body>
</html>