// JavaScript Document
var operator = "*";
function changeRate(p_this)
{
	var idx = p_this.selectedIndex;
  document.getElementById("txtRate").value = rates[idx];
  calculate();
}

function commaFormatted(amount)
{
	var a = amount.split('.', 2);
	var d = new String(a[1]);
	var i = parseInt(a[0]);
	if(isNaN(i))
	{
		return 'N/A';
	}
	
	var minus = '';
	if(i < 0)
	{
		minus = '-';
	}
	
	i = Math.abs(i);
	var n = new String(i);
	var b = [];
	while(n.length > 3)
	{
		var nn = n.substr(n.length-3);
		b.unshift(nn);
		n = n.substr(0,n.length-3);
	}
	
	if(n.length > 0)
	{
		b.unshift(n);
	}
	
	n = b.join(",");
	
	if(a[1])
	{
    if(d.length < 1)
    {
    	amount = n;
    }
    else
    {
    	amount = n + '.' + d;
    }
	}
	else
	{
		amount = n;
	}
	
	amount = minus + amount;
	
	return amount;
}

function calculate()
{
	var rate = parseFloat(document.getElementById("txtRate").value);
	var num = parseFloat(document.getElementById("num").value);
	var res = document.getElementById("res");
	var result = 'N/A';
	switch (operator)
	{
  	case "+":
    	result = rate + num;
    break;
    case "-":
    	result = rate - num;
   	break;
    case "*":
    	result = rate * num;
   	break;
    case "/":
    	result = rate / num;
    break;
	}
  res.value = commaFormatted(new String(result));
}

function changeOperator(op)
{
	operator = op;
	calculate();
}

function resetCalc()
{
	operator = "*";
  document.getElementById("changeRate").selectedIndex = 0;
  document.getElementById("num").value = 0;
  document.getElementById("txtRate").value = rates[0];
  calculate();
}