Common Javascript Functions for Financial Calculations

 /***********************************************
  *              Present Value                  *
  * pv = fv / (1 + (rate / freq))^periods       *
  * pv = Present Value                          *
  * fv = Future Value                           *
  * rate = interest rate (expressed as %)       *
  * freq = compounding frequency                *
  * periods = number of periods until maturity  *
  ***********************************************/
function presentValue(fv, freq, rate, periods)
{
    return (fv / Math.pow((1 + (rate / 100 / freq)), periods));
}

 /************************************************
  *                Future Value                  *
  * fv = pv * (1 + (rate / freq))^periods        *
  * fv = Future Value                            *
  * pv = Present Value                           *
  * rate = interest rate (expressed as %)        *
  * freq = compounding frequency                 *
  * periods = number of periods until maturity   *
  ************************************************/
function futureValue(pv, freq, rate, periods)
{
    return (pv * Math.pow(1 + (rate / 100 / freq), periods));
}

 /************************************************
  *            Annualized Return                 *
  * r = (fv - pv) / pv / years                   *
  * fv = future value                            *
  * pv = present value                           *
  * years = term of loan in years                *
  ************************************************/
function annualizedReturn(fv, pv, years)
{
    return (fv - pv) / pv / years;
}

function monthlyPayment(pv, freq, rate, periods)
{
    rate = rate / 100 / freq;
    
    var x = Math.pow(1 + rate, periods);
    return (pv * x * rate) / (x - 1);
}

 /***********************************************
  *                 Annuity                     *
  * a = fv / (((1 + r / c)^n) - 1) / (r/c)      *
  * fv = future value                           *
  * r = interest rate                           *
  * c = compounding frequency                   *
  * n = total number of periods                 *
  ***********************************************/  
function annuity(fv, freq, rate, periods)
{
    rate = rate / 100 / freq;
    return (fv / ((Math.pow(1 + rate, periods) - 1)) * rate);
}

function calcAmortPrincipal(pymt, freq, rate, periods)
{
    rate = rate / 100 / freq;
    return (pymt * (1 - (1 / Math.pow(1 + rate, periods))) / rate);
}

function regularDeposit(payment, freq, rate, periods)
{
    rate = rate / 100 / freq;
    return (payment * (Math.pow(1 + rate, periods) - 1) / rate * (1 + rate));
}

 /***********************************************
  *  Convert to currency notation               *
  ***********************************************/
function toCurrency(num) {
    num = Math.round(num * 100) * 0.01;
    var currstring = num.toString();
    if (currstring.match(/\./)) {
        var curr = currstring.split('.');
    } else {
        var curr = [currstring, "00"];
    }
    curr[1] += "00";
    curr[2] = "";
    var returnval = "";
    var length = curr[0].length;
    
    // add 0 to decimal if necessary
    for (var i = 0; i < 2; i++) 
        curr[2] += curr[1].substr(i, 1);
 
    // insert commas for readability
    for (i = length; (i - 3) > 0; i = i - 3) {
        returnval = "," + curr[0].substr(i - 3, 3) + returnval;
    }
    returnval = curr[0].substr(0, i) + returnval + "." + curr[2];
    return(returnval);
}