javascript验证邮件地址和MX记录的方法

// Tests for a valid email address and optionally tests for valid MX records, too.function is_valid_email($email, $test_mx = false){  if(eregi("^([_a-z0-9-]+)(/.[_a-z0-9-]+)*@([a-z0-9-]+)(/.[a-z0-9-]+)*(/.[a-z]{2,4})$", $email))    if($test_mx)    {      list($username, $domain) = split("@", $email);      return getmxrr($domain, $mxrecords);    }    else      return true;  else    return false;}