<!DOCTYPE html>
<html>
<head>
<title>JavaScript Loan Calculator
</title>
<style>
.output{
font-weight: bold;
}
#payment{
text-decoration: underline;
}
#graph{
border:solid black 1px;
}
th,td{
vertical-align: top;
}
</style>
</head>
<body>
<table>
<tr>
<th>Enter loan Data:
</th>
<td></td>
<th>Loan Balance,Cumulative Equity,and Interest Payments
</th>
</tr>
<tr>
<td>Amount of the loan($):
</td>
<td><input id="amount" onchange="calculate();"></td>
<td rowspan="8"><canvas id="graph" width="400" height="250"></canvas></td>
</tr>
<tr>
<td>Annual interest(%):
</td>
<td><input id="apr" onchange="calculate();"></td>
</tr>
<tr>
<td>Repayment period (years):
</td>
<td><input id="years" onchange="calculate();"></td>
</tr>
<tr>
<td>Zipcode (to find lenders):
</td>
<td><input id="zipcode" onchange="calculate();"></td>
</tr>
<tr>
<td>Approximate Payments
</td>
<td><button onclick="calculate();">Calculate
</button></td>
</tr>
<tr>
<td>Monthly payment:
</td>
<td>$
<span class="output" id="payment"></span></td>
</tr>
<tr>
<td>Total payment:
</td>
<td>$
<span class="output" id="total"></span></td>
</tr>
<tr>
<td>Total interest:
</td>
<td>$
<span class="output" id="totalinterest"></span></td>
</tr>
<tr>
<th>Sponsors:
</th>
<td rowspan="2">Apply for your loan width one of these fine lenders:
<div id="lenders"></div>
</td>
</tr>
</table>
<script>
function calculate(){
var amount=document.getElementById("amount");
var apr=document.getElementById("apr");
var years=document.getElementById("years");
var zipcode=document.getElementById("zipcode");
var payment=document.getElementById("payment");
var total=document.getElementById("total");
var totalinterest=document.getElementById("totalinterest");
var principal=parseFloat(amount.value);
var interest=parseFloat(apr.value)/100/12;
var payments=parseFloat(years.value)*12;
var x=Math.pow(1+interest,payments);
var monthly=(principal*x*interest)/(x-1);
if(isFinite(monthly)){
payment.innerHTML=monthly.toFixed(2);
total.innerHTML=(monthly*payments).toFixed(2);
totalinterest.innerHTML=((monthly*payments)-principal).toFixed(2);
save(amount.value,apr.value,years.value,zipcode.value);
try{
getLenders(amount.value,apr.value,years.value,zipcode.value);
}catch(e){
console.log(e);
}
chart(principal,interest,monthly,payments);
}else{
payment.innerHTML="";
total.innerHTML="";
totalinterest.innerHTML="";
chart();
}
}
function save(amount,apr,years,zipcode){
if(window.localStorage){
localStorage.loan_amount=amount;
localStorage.loan_apr=apr;
localStorage.loan_years=years;
localStorage.loan_zipcode=zipcode;
}
}
window.onload=function(){
if(window.localStorage&&localStorage.loan_amount){
document.getElementById("amount").value=localStorage.loan_amount;
document.getElementById("apr").value=localStorage.loan_apr;
document.getElementById("years").value=localStorage.loan_years;
document.getElementById("zipcode").value=localStorage.loan_zipcode;
}
}
function getLenders(amount,apr,years,zipcode){
if(!window.XMLHttpRequest){
return;
}
var ad=document.getElementById("lenders");
if(!ad){
return;
}
var url="getLenders.php"+
"?amt="+encodeURIComponent(amount)+
"&apr="+encodeURIComponent(apr)+
"&yrs="+encodeURIComponent(years)+
"&zip="+encodeURIComponent(zipcode);
var req=new XMLHttpRequest();
req.open("GET",url);
req.send(null);
req.onreadystatechange=function(){
if(req.readyState==4&&req.status==200){
var response=req.responseText;
var lenders=JSON.parse(response);
var list="";
for(var i=0;i<lenders.length;i++){
list+="<li><a href='"+lenders[i].url+"'>"+lenders[i].name+"</a></li>";
}
ad.innerHTML="<ul>"+list+"</ul>";
}
}
}
function chart(principal,interest,monthly,payments){
var graph=document.getElementById("graph");
graph.width=graph.width;
if(arguments.length==0||!graph.getContext){
return;
}
var g=graph.getContext("2d");
var width=graph.width;
var height=graph.height;
function paymentToX(n){
return n*width/payments;
}
function amountToY(a){
return height-(a*height/(monthly*payments*1.05));
}
g.moveTo(paymentToX(0),amountToY(0));
g.lineTo(paymentToX(payments),amountToY(monthly*payments));
g.lineTo(paymentToX(payments),amountToY(0));
g.closePath();
g.fillStyle="#f88";
g.fill();
g.font="bold 12px sans-serif";
g.fillText("Total Interest Payments",20,20);
var equity=0;
g.beginPath();
g.moveTo(paymentToX(0),amountToY(0));
for(var p=1;p<=payments;p++){
var m=(principal-equity)*interest;
equity+=(monthly-m);
g.lineTo(paymentToX(p),amountToY(equity));
}
g.lineTo(paymentToX(payments),amountToY(0));
g.closePath();
g.fillStyle='green';
g.fill();
g.font="bold 12px sans-serif";
g.fillText("Total Equity",20,35);
var bal=principal;
g.beginPath();
g.moveTo(paymentToX(0),amountToY(bal));
for(var p=1;p<=payments;p++){
var m=bal*interest;
bal-=(monthly-m);
g.lineTo(paymentToX(p),amountToY(bal));
}
g.lineWidth=1;
g.stroke();
g.fillStyle="black";
g.fillText("Loan Balance",20,50);
g.textAlign="center";
var y=amountToY(0);
for(var year=1;year*12<=payments;year++){
var x=paymentToX(year*12);
g.fillRect(x-0.5,y-3,1,3);
if(year==1){
g.fillText("Year",x,y-5);
}
if(year%5==0&&year*12!=payments){
g.fillText(String(year),x,y-5);
}
}
g.textAlign="right";
g.textBaseline="middle";
var ticks=[monthly*payments,principal];
var rightEdge=paymentToX(payments);
for(var i=0;i<ticks.length;i++){
var y=amountToY(ticks[i]);
g.fillRect(rightEdge-3,y-0.5,3,1);
g.fillText(String(ticks[i].toFixed(0)),rightEdge-5,y);
}
}
</script>
</body>
</html>
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