annuity-due.js

const calculateInterest = ({
  initialAmount = 0,
  additionalPerYear = 0,
  interestRate = 0,
  years = 0,
} = {}) => {
  const annuityDue = interestRate / (interestRate + 1)

  const x = (initialAmount + (additionalPerYear / annuityDue))
  const y = Math.pow(1 + interestRate, years)
  const z = additionalPerYear / annuityDue

  return ((x * y) - z)
}