function checkMail(str){
	if(!checkCHR(str)) return false;
	var valid = false;
	var reg1 = /(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/; // not valid
	var reg2 = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/; // valid
	if (!reg1.test(str) && reg2.test(str) && str != "") { // if syntax is valid
		return true;
	}
	else return false;
}

// a whole number greater than zero
function checkNumber(_num){
	if(isNaN(_num)) return false;
	if(_num < 1) return false;
	if(Math.floor(_num) != _num) return false;
	return true;
}

function checkPhone(phone){
	if(phone.length < 4) return false;
	var invalid_chars = /[^0-9\.\-\/\(\)\\\+\=\s]/;
	if(invalid_chars.test(phone)) return false;
	return true;
}

// chars allowd in email (a-z A-Z 0-9 - _ . @)
function checkCHR(str){
	var wrong = /[^A-Za-z0-9_\-|\@|\.]/; // forbidden characters
	if(wrong.test(str)) return false;
	else return true;
}