Converting future value calculation of compound interest calculator to javascript

Question

I am currently trying to convert an equation in google sheets to Javascript but I am getting different results.

I am trying to replicate the following formula from here:

Original equation:

F = P*(1+rate)^nper + A*( ((1+rate)^nper - 1)/rate )

This is what I currently have: (In my actual code snippet below names of variables are different)

v = ((p*(Math.pow((1+rate),nper))) + (A*(Math.pow((1+rate),nper - 1))/rate));

Extra Information from original site:
r = nominal annual interest rate (decimal)
n = number of compounding periods per year
p = number of payment periods per year
rate = rate per payment period
nper = total number of payment periods
A = an amount added to the principal at the end of each payment period

rate = ((1+r/n)^(n/p))-1
nper = p * t
Total Payments = A*nper
Total Interest = F - P - Total Payments

Full context (My Vue Code):

        var app = new Vue({
          el: '#app',
          data: {
            principal: 0,
            interest_rate: 0,
            time_invested: 0,
            additional_investment: 0,
            additional_investment_frequency : 1,
            options: {
                additional_investment_frequency: {
                "1": "Yearly",
                "12": "Monthly",
                "26": "Fortnightly",
                "52": "Weekly",
                "365": "Daily"
                }
            },
            compound_frequency : 1,
            options: {
                compound_frequency: {
                "1": "Yearly",
                "12": "Monthly"
                }
            }
          },
          methods:{
        },
          computed: {
            total_pay_periods: function () {
                // calculate total number of pay periods
                total_pay_periods = parseFloat(this.additional_investment_frequency) * parseFloat(this.time_invested);
                return parseFloat(this.additional_investment_frequency) * parseFloat(this.time_invested);
            },
            total_additional_investment: function () {
                // calculate total number of pay periods
                total_pay_periods = parseFloat(this.additional_investment_frequency) * parseFloat(this.time_invested);
                // times total pay periods by additional investment installment amount to get overall total additional investment
                return parseFloat(this.additional_investment) *  total_pay_periods;
            },
            rate: function () {
                ir = parseFloat(this.interest_rate) / 100;
                cf = parseFloat(this.compound_frequency);
                aif = parseFloat(this.additional_investment_frequency);
                return (Math.pow((1+ir/cf),(cf/aif))-1);
                // return (((1+ir/cf)^(cf/aif))-1);
            },
            future_value: function () {
                p = parseFloat(this.principal);
                r = parseFloat(this.rate);
                tpp = parseFloat(this.total_pay_periods);
                ai = parseFloat(this.additional_investment);

                // F = P*(1+rate)^nper + A*( ((1+rate)^nper - 1)/rate )
                // https://www.vertex42.com/Calculators/compound-interest-calculator.html#rate-per-period

                // calculate final future value
                v = ((p*(Math.pow((1+r),tpp))) + (ai*(Math.pow((1+r),tpp - 1))/r));
                // convert to 2 decimal places
                return  v.toFixed(2);
            }
          }
        })

Answer 1

There is a mistake in your second term (A*(Math.pow((1+rate),nper - 1))/rate)); the -1 is going to the power function. Correct way would be (A*(Math.pow((1+rate),nper) - 1)/rate));