Mortgage Payment Calculator Extra Payment

let mortgageSteps = “”; const currencySymbol = “$”, fixedCurrency = “USD”; function calculateMortgage(){ mortgageSteps=””; const loanAmount=parseFloat(document.getElementById(“loanAmount”).value); const interestRate=parseFloat(document.getElementById(“interestRate”).value)/100/12; const loanTerm=parseInt(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) / (1 – Math.pow(1 + interestRate, -loanTerm)); const newMonthlyPayment = monthlyPayment + extraPayment; const totalInterest = (newMonthlyPayment * loanTerm) – loanAmount; const yearsPaidOff = loanTerm / 12; document.getElementById("monthlyPayment").value = formatCurrency(newMonthlyPayment); document.getElementById("totalInterest").value = formatCurrency(totalInterest); document.getElementById("loanPaidOff").value = yearsPaidOff.toFixed(1); mortgageSteps += `Inputs:
Loan Amount: ${formatCurrency(loanAmount)}
Interest Rate: ${(interestRate*12*100).toFixed(2)}%
Loan Term: ${loanTerm/12} years
Extra Monthly Payment: ${formatCurrency(extraPayment)}

`; mortgageSteps += `Formulas:
Monthly Payment = (Loan Amount × Interest Rate) / (1 – (1 + Interest Rate)^(-Loan Term))
Total Interest = (Monthly Payment × Loan Term) – Loan Amount
Loan Paid Off In = Loan Term / 12

`; mortgageSteps += `Results:
Estimated Monthly Payment: ${formatCurrency(newMonthlyPayment)}
Total Interest Paid: ${formatCurrency(totalInterest)}
Loan Paid Off In: ${yearsPaidOff.toFixed(1)} years
`; if(document.getElementById(“calculationStepsMortgage”).style.display===”block”){ document.getElementById(“calculationStepsMortgage”).innerHTML = mortgageSteps; } } function resetMortgage(){ document.querySelectorAll(“#calculator input”).forEach(el=>el.value=””); mortgageSteps=””; document.getElementById(“calculationStepsMortgage”).innerHTML=”

Not calculated yet.

“; } function toggleMortgageSteps(){ const s=document.getElementById(“calculationStepsMortgage”); const a=document.getElementById(“toggleArrowMortgage”); if(s.style.display===”none”||s.style.display===””){ s.style.display=”block”;a.style.transform=”rotate(180deg)”; s.innerHTML=mortgageSteps||”

Not calculated yet.

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