let calcSteps = “”; const currencySymbol = “$”, fixedCurrency = “USD”; function calculateExtraPayments() { calcSteps = “”; const loanAmount = parseFloat(document.getElementById(“loanAmount”).value); const interestRate = parseFloat(document.getElementById(“interestRate”).value) / 100; const loanTerm = parseFloat(document.getElementById(“loanTerm”).value) * 12; const extraPayment = parseFloat(document.getElementById(“extraPayment”).value); if (isNaN(loanAmount) || isNaN(interestRate) || isNaN(loanTerm) || isNaN(extraPayment) || loanAmount <= 0 || interestRate <= 0 || loanTerm <= 0) { alert("Please enter valid positive values for all fields."); return; } const monthlyPayment = (loanAmount * interestRate / 12) / (1 – Math.pow(1 + interestRate / 12, -loanTerm)); const newLoanTerm = Math.log((extraPayment + monthlyPayment) / (extraPayment + monthlyPayment – loanAmount * interestRate / 12)) / Math.log(1 + interestRate / 12); const totalSavings = (monthlyPayment * loanTerm) – (extraPayment * newLoanTerm); const yearsLeft = newLoanTerm / 12; document.getElementById("savingsResult").value = formatCurrency(totalSavings); document.getElementById("loanPayoffTime").value = yearsLeft.toFixed(2); calcSteps += `Inputs:
Loan Amount: ${formatCurrency(loanAmount)}
Interest Rate: ${(interestRate * 100).toFixed(2)}%
Loan Term: ${loanTerm / 12} years
Extra Payment: ${formatCurrency(extraPayment)}

`; calcSteps += `Formulas:
Monthly Payment = Loan Amount × Interest Rate / 12
New Loan Term = Log((Extra Payment + Monthly Payment) / (Extra Payment + Monthly Payment – Loan Amount × Interest Rate / 12)) / Log(1 + Interest Rate / 12)

`; calcSteps += `Results:
Total Savings: ${formatCurrency(totalSavings)}
Loan Payoff Time: ${yearsLeft.toFixed(2)} years
`; if (document.getElementById(“calculationSteps”).style.display === “block”) { document.getElementById(“calculationSteps”).innerHTML = calcSteps; } } function resetCalculator() { document.querySelectorAll(“#calculator input”).forEach(el => el.value = “”); calcSteps = “”; document.getElementById(“calculationSteps”).innerHTML = “

Not calculated yet.

“; } function toggleCalculationSteps() { const steps = document.getElementById(“calculationSteps”); const arrow = document.getElementById(“toggleArrow”); if (steps.style.display === “none” || steps.style.display === “”) { steps.style.display = “block”; arrow.style.transform = “rotate(180deg)”; steps.innerHTML = calcSteps || “

Not calculated yet.

“; } else { steps.style.display = “none”; arrow.style.transform = “rotate(0deg)”; } } function formatCurrency(n) { return currencySymbol + n.toFixed(2) + ” ” + fixedCurrency; }