jsフォームの検証

<script language="javascript">
function isEmail(strEmail) {
  if (strEmail.search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/) != -1)
   return true;
  else
   alert("Email     ！");
   document.formSignUp.email.value="";
   document.formSignUp.email.focus();
 }
</script>
<input onblur="isEmail(this.value)">