function isValidEmail(email) {
	var filter = /^([a-zA-Z0-9_.-])+@(([a-zA-Z0-9-])+.)+([a-zA-Z0-9]{2,4})+$/;
	if (!filter.test(email)) {
		return false;
	} else {
		return true;
	}
}

function isValidUsername(username) {
	var pattern = /^[a-zA-Z0-9_]{4,}$/;
	if (!pattern.test(username)) {
		return false;
	} else {
		return true;
	}
}