<script type="text/javascript">
 var sText = document.getElementById('mail').value;
//onblur 為控件失去焦點事件
 document.getElementById('mail').onblur = function sValue(){
 sText = this.value;
 var reMail =/^(?:[a-zA-Z0-9]+[_\-\+\.]?)*[a-zA-Z0-9]+@(?:([a-zA-Z0-9]+[_\-]?)*[a-zA-Z0-9]+\.)+([a-zA-Z]{2,})+$/;
 var s=new RegExp(reMail);
 if(s.test(sText))
 {alert("郵箱正確");}
 else//不正確清空
 {document.getElementById('mail').value="";}
 }
</script>