检测八位数字是否为有效日期的正则

<meta http-equiv="Content-Type" content="text/html;charset=UTF-8"> <title>测试八位数字是否为有效日期</title> <div> <span>string : </span><input id="str1" type="text" value="19990228" size="100"><span>regex : </span><input id="str2" type="text" value="^(?:(?:(?:(?=\d{2}(?:(?:[02468][048])|(?:[13579][26])))\d{4}02(?!00)[0-2]\d))|(?:\d{4}(?:(?:(?:(?:0[469])|(?:11))(?!00)(?:(?:[0-2]\d)|(?:30)))|(?:(?:(?:0[13578])|(?:1[02]))(?!00)(?:(?:[0-2]\d)|(?:3[01])))|(?:02(?!(?:00)|(?:29))[0-2]\d))))$" size="100"><input type="button" value="ok" onclick="javascript:fun2();"> </div>
[ctrl+a 全选 注:如需引入外部js需刷新才能执行]