function chkNumber(input, min, max, fieldName, mayBeBlank) {
msg = 'The ' + fieldName + ' field';
if (input.value == null || input.value.length == 0) {
if (mayBeBlank == "yes") {
return true;
}
alert(msg + ' must be filled in!');
input.focus();
input.select();
return false;
}
var str = input.value;
for (var i = 0; i < str.length; i++) {
var ch = str.substring(i, i + 1);
if ((ch < "0" || "9" < ch) && ch != '.') {
if (ch != '%' || i != str.length - 1) {
alert(msg + ' has a non-numeric character');
input.focus();
input.select();
return false;
}
}
}
var num = parseFloat(str);
if (num < min || max < num) {
alert(msg + ' must be between [' + min + ".." + max + "]");
input.focus();
input.select();
return false;
}
return true;
}
function changeAmount(field) {
var amt = field.form.amount.value == null || field.form.amount.value.length == 0 ? 0 : field.form.amount.value;
var down = field.form.downpymt.value == null || field.form.downpymt.value.length == 0 ? 0 : field.form.downpymt.value;
var price = field.form.purchase.value == null || field.form.purchase.value.length == 0 ? 0 : field.form.purchase.value;
if (!chkNumber(field.form.amount, 0, 999999999, "Loan Amount", "yes") ||
!chkNumber(field.form.purchase, 0, 999999999, "Purchase Price", "yes") ||
!chkNumber(field.form.downpymt, 0, price, "Down Payment", "yes")) {
return;
}
if (field.name == "amount") {
if (down != 0 && price - amt >= 0) {
field.form.downpymt.value = price - amt;
} else {
field.form.purchase.value = amt - -down;
}
} else {
field.form.amount.value = price - down;
}
}
function round(value, places) {
var chars = (places == 0 ? 0 : places + 1);
var str = "" + value;
for (var i = 0; (str.substring(i, i + 1) != "." && i < str.length); ++i) {
}
if (i == 0) {
return str;
}
if (i < 4) {
return(str.substring(0, i + chars));
}
var retstr = "";
for(j = 0; j < i; ++j) {
if (j != 0 && (i-j) % 3 == 0) {
retstr = retstr + ",";
}
retstr = retstr + str.substring(j, j + 1);
}
retstr = retstr + str.substring(i, i + chars);
return retstr;
}
function calculatePayment(amt, rate, months) {
if (rate <= 0) {
return "0.00";
}
rate /= 1200.0;
var power = 1.0;
for (var i=0; ++i <= months; power *= (1 + rate)) {
}
return amt * (rate / (1 - (1 / power)));
}
function computeForm(form,name,ismort /* ismort is true for CMORT, false for CLOAN */) {
if (!chkNumber(form.amount, 1000, 999999999, "Loan Amount", "no") ||
!chkNumber(form.rate, 0.01, 19.99, "Interest Rate", "no") ||
!chkNumber(form.months, 1, 72, "Number of Months", "no") ||
!chkNumber(form.years, 1, 50, "Number of Years", "no") ||
!chkNumber(form.cap, 0, 10, "ARM Cap", "yes")) {
return;
}
if (form.rate.value < 1.0) {
form.rate.value = form.rate.value * 100;
}
var months = ismort ? form.years.value * 12 : form.months.value;
var monthpay = calculatePayment(form.amount.value, form.rate.value, months);
var docmessage;
docmessage = "Your monthly payment will be $" + round(monthpay, 2) + ".
";
docmessage = docmessage + "Your total payments will be $" + round(monthpay * months,2) + ".
";
docmessage = docmessage + "Your total interest paid will be $" + round((monthpay * months) - form.amount.value, 2) + ".
";
if (form.cap.value != null && form.cap.value.length != 0 && form.cap.value != 0) {
if (form.cap.value < 1.0) {
form.cap.value = form.cap.value * 100;
}
docmessage = docmessage + "With an Adjustable Rate Mortgage and a lifetime cap of +/-" + form.cap.value + "%:";
docmessage = docmessage + "- Your lowest possible monthly payment would be $" + round(calculatePayment(form.amount.value,
form.rate.value - form.cap.value,
months), 2) + "
";
docmessage = docmessage + "Your highest possible monthly payment would be $" + round(calculatePayment(form.amount.value,
form.rate.value - -form.cap.value,
months), 2) + "
";
}
docmessage = docmessage + "Amortization schedule (at " + form.rate.value + "%):
";
docmessage = docmessage + "";
docmessage = docmessage + "| " + (ismort ? "Year" : "Month") + " | ";
docmessage = docmessage + "Principal Paid | ";
docmessage = docmessage + "Interest Paid | ";
docmessage = docmessage + "Remaining Balance |
";
var k = form.rate.value / 1200;
var m = 1;
var y = 1;
var bal = form.amount.value;
var pp = 0;
var ip = 0;
var yip = 0;
var ypp = 0;
var i = 0;
for(i = 0; ++i <= months;) {
ip = bal * k;
yip += ip;
pp = monthpay - ip;
ypp += pp;
bal -= i == months ? bal : pp;
if (!ismort) {
docmessage = docmessage + "| " + i + " | ";
docmessage = docmessage + "$" + round(pp, 2) + " | ";
docmessage = docmessage + "$" + round(ip, 2) + " | ";
docmessage = docmessage + "$" + round(bal, 2) + " |
";
}
if (m++ == 12) {
if (ismort) {
docmessage = docmessage + "| " + y + " | ";
docmessage = docmessage + "$" + round(ypp, 2) + " | ";
docmessage = docmessage + "$" + round(yip, 2) + " | ";
docmessage = docmessage + "$" + round(bal, 2) + " |
";
} else {
docmessage = docmessage + "| Interest paid in year " + y + " is $" + round(yip, 2) + " |
|---|
";
}
yip = 0;
ypp = 0;
m = 1;
++y;
}
}
if (!ismort && m != 1) {
docmessage = docmessage + "| Interest paid for year " + y + " is $" + round(yip, 2) + " |
|---|
";
}
docmessage = docmessage + "
";
result.innerHTML = docmessage;
}