var a = 0; function disableAmort() { document.forms[0].amortization.disabled = true; } function computeLoan() { if (validateCalcForm()) { var p = parseFloat(document.forms[0].balance.value); var r = (parseFloat(document.forms[0].interest.value)/100)/12; var n = parseFloat(document.forms[0].termlength.value); a = (p * (Math.pow((1 + r), n)) * r)/((Math.pow((1 + r), n)) - 1); var payment = a; payment = Math.round(payment * 100); payment = payment / 100; payment = payment.toString(); if (payment.length > payment.indexOf(".") + 2) { payment = payment.substring(0, (payment.indexOf(".") + 3)) } document.forms[0].payment.value = payment; document.forms[0].amortization.disabled = false; } } function doAmortization() { var balance = document.forms[0].balance.value; payment = a; var interest = (parseFloat(document.forms[0].interest.value)/100)/12; if (isNaN(parseInt(document.forms[0].extra.value))) { var extra = 0; } else { var extra = (parseFloat(document.forms[0].extra.value)); } var thisInterest = 0; var thisPrincipal = 0; var newBalance = 0; var paymentCounter = 1; var totalInterest = 0; scheduleWindow = window.open("", "","scrollbars,resizable,width=570"); scheduleWindow.focus(); scheduleWindow.document.write('Amortization Schedule - Math·U·See'); scheduleWindow.document.write('
'); for (var thisBalance = balance; (!(thisBalance <= 0));) { scheduleWindow.document.write(''); if (newBalance == 0) { scheduleWindow.document.write('

Amortization Schedule

Payment numberPrincipalInterestNew Balance
' + paymentCounter); thisInterest = (thisBalance * interest); thisPrincipal = (payment - thisInterest) + extra; newBalance = (thisBalance - thisPrincipal); totalInterest += thisInterest; if (newBalance <= 0) { thisPrincipal = (thisPrincipal + newBalance); newBalance = 0; } scheduleWindow.document.write('' + format(thisPrincipal) + '' + format(thisInterest) + '' + format(newBalance) + '
Total interest paid = ' + format(totalInterest) + '
'); } paymentCounter += 1; thisBalance = newBalance; } scheduleWindow.document.write('
'); scheduleWindow.document.close(); } function format(thisNumber) { thisNumber = (Math.round(thisNumber * 100) / 100); thisNumber = thisNumber.toString(); if (thisNumber.indexOf(".") == -1) { thisNumber = thisNumber + "." + "00"; } if (thisNumber.length - thisNumber.indexOf(".") == 2) { thisNumber = thisNumber + "" + "0"; } return thisNumber; } function validateCalcForm() { if (isNaN(parseInt(document.forms[0].balance.value)) || isNaN(parseInt(document.forms[0].interest.value)) || isNaN(parseInt(document.forms[0].termlength.value))) { alert("Please fill in the top 3 text fields using numeric values."); var bad = true; } if (bad == true) { return false; } return true; }