var request = createXmlHttpRequestObject();
function createXmlHttpRequestObject() {
  var request = null;

   try {
     request = new XMLHttpRequest();
   } catch (trymicrosoft) {
     try {
       request = new ActiveXObject("Msxml2.XMLHTTP");
     } catch (othermicrosoft) {
       try {
         request = new ActiveXObject("Microsoft.XMLHTTP");
       } catch (failed) {
         request = null;
       }
     }
   }

   if (request == null){
     alert("Error creating request object!");
	}else{
	 return request;
	}
}

function addtonewsletter() {
	var email = document.getElementById('newsletteremail').value;
	var control = validateEmail(email);
if(control){
			var url = "templates/newsletter_submit.php?email=" +escape(email);
			request.open("GET", url, true);
			request.onreadystatechange = newsletterajaxreply;
			request.send(null);
}else {
	alert("Η μορφή του e-mail δεν είναι έγκυρη");
}
}

function newsletterajaxreply() {
	if (request.readyState == 4) {
		if (request.status == 200) {
			responsetext = request.responseText;
			if (responsetext.indexOf('OK:') > -1) {
				responsetext = responsetext.replace('OK:', '');
				alert(responsetext);
			} else if (responsetext.indexOf('WARNING:') > -1) {
				responsetext = responsetext.replace('WARNING:', '');
				alert(responsetext);
			} else if (responsetext.indexOf('ERROR:') > -1) {
				responsetext = responsetext.replace('ERROR:', '');
				alert(responsetext);
			}
		}
	}
}

function validateEmail(elementValue){  
	var emailPattern = /^[a-zA-Z0-9._-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$/;  
	return emailPattern.test(elementValue);  
}

function clearText(obj){
	if (obj.defaultValue == obj.value) {
		obj.value = '';
	} else if (obj.value == '') {
		obj.value = obj.defaultValue;
	}
}