function isValid() {
	var code = document.getElementById('code');
	if(!isEmpty(code, "Please, enter a code / Introduzca un código")){
		if(isAlphabet(code, "Only letters allowed / solo letras permitidas")){
			return true;
		}
	}
		
	return false;
		
}

function isEmpty(elem, helperMsg){
	if(elem.value.length == 0){
		alert(helperMsg);
		elem.focus();
		return true;
	}
	return false;
}

function isAlphabet(elem, helperMsg){
	var alphaExp = /^[a-zA-Z]+$/;
	if(elem.value.match(alphaExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}