菜鸟教程在线编辑器

 
                <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<h2>JavaScript Error 对象</h2>
<p>您不能将数字的有效位数设置为 500:</p>

<p id="demo">

<script>
var num = 1;
try {
    num.toPrecision(500);
}
catch(err) {
    document.getElementById("demo").innerHTML = err.name;
}
</script>

</body>
</html>
              