JavaScript验证邮箱的合法性

<script type="text/javascript">
 var sText = document.getElementById('mail').value;
//onblur 为控件失去焦点事件
 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("邮箱正确");}
  else//不正确清空
 {document.getElementById('mail').value="";}
 }
</script>