js校验邮箱

<script type="text/javascript">function isEmail(str){       var reg = /^([a-zA-Z0-9_-])+@([a-zA-Z0-9_-])+((\.[a-zA-Z0-9_-]{2,3}){1,2})$/;       alert( reg.test(str));}</script><input id="zz" type="text"/><input type="button" onclick="isEmail(zz.value)"/>