<script type="text/javascript">
  var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
  var mail = "goragod@yahoo.com"
  if (!filter.test(mail)) alert("อีเมล์ไม่ถูกต้อง")
  else alert("ขอบคุณ " + mail)
</script>