function calculate_payment(PV, IR, NP) {
    if (IR == 0) {
        var rnd = round_decimals(PV / NP, 2)
        return formatCurrency(rnd);
    }
    else {
        var PMT = (PV * IR) / (1 - Math.pow(1 + IR, -NP))

        var rnd = round_decimals(PMT, 2)
        return formatCurrency(rnd);
    }
}

function round_decimals(original_number, decimals) {
    var result1 = original_number * Math.pow(10, decimals)
    var result2 = Math.round(result1)
    var result3 = result2 / Math.pow(10, decimals)
    return (result3)
}

function calcMonthlyPymt() {
    var present_value = document.getElementById("loanAmt").value;
    var interest_rate = document.getElementById("apr").value / 100;
    var loan_term = document.getElementById("loanTerm").value;

    var present_value_str = present_value.substr(1);
    present_value_str = present_value_str.replace(/,/, "");

    var monthly_payment = calculate_payment(present_value_str, interest_rate / 12, loan_term); //* 12

    document.getElementById("MonthlyPymt").value = monthly_payment;

    document.getElementById("txtLoanAmt").value = "";
    document.getElementById("txtApr").value = "";
    document.getElementById("txtLoanTerm").value = "";
    document.getElementById("txtMonthlyPymt").value = "";

    window.open(
    "calculators.aspx?" + "apr=" + interest_rate * 100 + "&loanTerm=" + loan_term + "&loanAmt=" + present_value_str + "&monthlyPymt=" + monthly_payment
    + "&apr1=" + "" + "&loanTerm1=" + "" + "&loanAmt1=" + "" + "&monthlyPymt1=" + "", "_self");
}

function calculate_payment1(PMT, IR, NP) {
    if (IR == 0) {
        var rnd1 = round_decimals(PMT * NP, 2)
        return formatCurrency(rnd1);
    }
    else {
        var PV = (PMT * (1 - Math.pow(1 + IR, -NP))) / IR

        var rnd1 = round_decimals(PV, 2);
        return formatCurrency(rnd1);
    }
}

function calcMonthlyPymt1() {
    var monthly_payment1 = document.getElementById("MonthlyPymt1").value;

    monthly_payment1_str = monthly_payment1.substr(1);
    monthly_payment1_str = monthly_payment1_str.replace(/,/, "");

    var interest_rate1 = document.getElementById("apr1").value / 100;
    var loan_term1 = document.getElementById("loanTerm1").value;
    var present_value1 = calculate_payment1(monthly_payment1_str, interest_rate1 / 12, loan_term1); //* 12

    document.getElementById("loanAmt1").value = present_value1;

    document.getElementById("txtLoanAmt1").value = "";
    document.getElementById("txtApr1").value = "";
    document.getElementById("txtLoanTerm1").value = "";
    document.getElementById("txtMonthlyPymt1").value = "";


    window.open("http://" + '<%=Request.Url.Host%>' + "/resources/" +
   "calculators.aspx?" + "apr1=" + interest_rate1 * 100 + "&loanTerm1=" + loan_term1 + "&loanAmt1=" + present_value1 + "&monthlyPymt1=" + monthly_payment1
   + "&apr=" + "" + "&loanTerm=" + "" + "&loanAmt=" + "" + "&monthlyPymt=" + "" + "&show=1"
   , "_self");
}

function formatCurrency(num) {

    num = num.toString().replace(/\$|\,/g, '');
    //CurrencySymbol = “$”;

    if (isNaN(num))
        num = "0";
    sign = (num == (num = Math.abs(num)));
    num = Math.floor(num * 100 + 0.50000000001);
    cents = num % 100;
    num = Math.floor(num / 100).toString();
    if (cents < 10)
        cents = "0" + cents;
    for (var i = 0; i < Math.floor((num.length - (1 + i)) / 3); i++)
        num = num.substring(0, num.length - (4 * i + 3)) + ',' +
    num.substring(num.length - (4 * i + 3));

    return (((sign) ? '' : '-') + "$" + num + '.' + cents);
}