function trimR(str){
	while (str.substring(str.length-1,str.length) == ' ') {
		str = str.substring(0,str.length-1);
	}
	return str;
}
function trimL(str){
	while (str.substring(0,1) == ' ') {
		str = str.substring(1,str.length);
	}		
	return str;
}
function trim(str) {
	str = trimL(trimR(str));
	return str;
}

function isEmpty(obj){
	if(trim(obj).length <= 0){
		return true;
	}else{
		return false;
	}
}

function getObj(header) {
	return document.getElementById(header);
}

function showHide(header) {
	obj = getObj(header);
	if (obj.style.display=='') { obj.style.display='none'; }
	else {obj.style.display='';}
}

function PMT(payments_per_year, number_of_periods, annual_interest_rate, loan_amount){ 
	var payment_interest_rate = 1 / (1 + (annual_interest_rate/payments_per_year)); 
	return Math.ceil(  ((1 - payment_interest_rate) * loan_amount) / (payment_interest_rate * (1 - Math.pow(payment_interest_rate,number_of_periods)))); 
}