Excel PMT function in JS

Question

Hello!

I found i little snipet on internet, about PMT calculate.

function PMT(i, n, p) {
 return i * p * Math.pow((1 + i), n) / (1 - Math.pow((1 + i), n));
}
function CalculatePMTFromForm(idLoanAmount, idAnnualInterestRate, idMonths, idResult) {
 var i = jQuery('#' + idAnnualInterestRate).val() / 1200;
 var n = jQuery('#' + idMonths).val();
 var p = jQuery('#' + idLoanAmount).val();
 var pmt = PMT(i, n, -p);
jQuery('#' + idResult).val(pmt.toFixed(2));
}
function performCalc() {
 CalculatePMTFromForm('LoanAmount', 'InterestRate', 'Months', 'Payment');
}
jQuery(document).ready(function() { performCalc(); jQuery('.calc').keyup(performCalc); });

When the page is load, in the result input box I see "NaN" , and when i tpye some irrelevant number then "-Infinity" msg appear. I search to "NaN" in files and i found in jquery.js, but after I modify, nothing change. And I can't find Infinity

How can I change this messages?

Edit

Calling code:-

function performCalc() {
  CalculatePMTFromForm('LoanAmount', 'InterestRate', 'Months', 'Payment');
}

jQuery(document).ready(function() {
  performCalc(); jQuery('.calc').keyup(performCalc);
});

This is worked for me:

if(pmt>0 && pmt<Number.MAX_VALUE) {jQuery('#' + idResult).val(pmt.toFixed(2));}

Answer 1

NaN means "Not A Number".

Make sure you check for each input value whether it is numeric. Throw an error message if one is not, or set it to 0, depending on whether it's essential to your calculation or not.

A good collection of the best ways to check a value for whether it's numeric is this SO question: Validate numbers in JavaScript - IsNumeric()

Answer 2

Try it like this:-

function CalculatePMTFromForm(idLoanAmount, idAnnualInterestRate, idMonths, idResult) {
 var i = parseFloat($('#' + idAnnualInterestRate).val()) / 1200;
 var n = parseFloat($('#' + idMonths).val());
 var p = parseFloat($('#' + idLoanAmount).val());
 var pmt = PMT(i, n, -p);
 $('#' + idResult).val(pmt.toFixed(2));
}

The .val() is likely returning a string type not a number type.