How to Build a Home Loan Calculator

function calculateHomePayment(homePrice, downPayment, rate, years, taxRate, insurance) {
  const principal = homePrice - downPayment;
  const monthlyRate = rate / 100 / 12;
  const numPayments = years * 12;

  const pi = principal *
    (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) /
    (Math.pow(1 + monthlyRate, numPayments) - 1);

  const monthlyTax = (homePrice * taxRate / 100) / 12;
  const monthlyInsurance = insurance / 12;
  const pmi = downPayment < homePrice * 0.2 ? (principal * 0.01) / 12 : 0;

  return {
    principalInterest: pi,
    taxes: monthlyTax,
    insurance: monthlyInsurance,
    pmi: pmi,
    total: pi + monthlyTax + monthlyInsurance + pmi
  };
}