<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
    </head>
    <body>
        <h2></h2>

        <script>
            var person = {
                level: '2',
                name: '小丽',
                registTime: '2021-11-01',
            }
            var h2 = document.querySelector('h2');
            // 补全代码
            h2.innerHTML = '尊贵的牛客网'+person.level+'级用户小丽您好，您已经注册牛客网'+Math.floor((new Date() - new Date(person.registTime)) / (1000 * 60 * 60 * 24))+'天啦~'
        </script>
    </body>
</html>