console
$(document).ready(function(){
countPay();
function countPay(){
assessRate = $("#assessRate").val()/100;
loanRate = $("#loanRate").val()/100;
taxRate = $("#taxRate").val()/100;
agencyFeeRate = $("#agencyFeeRate").val()/100;
pay = $("#totalDownPayment").val();
totalpay = pay / (1-assessRate*loanRate+taxRate+agencyFeeRate)
loanAmount = totalpay*assessRate*loanRate;
taxAmount = totalpay*taxRate;
agencyFee = totalpay*agencyFeeRate;
downPayment = totalpay-loanAmount;
$("#total").text(totalpay.toFixed(2));
$("#loan").text(loanAmount.toFixed(2));
$("#tax").text(taxAmount.toFixed(2));
$("#agencyFee").text(agencyFee.toFixed(2));
$("#downPayment").text(downPayment.toFixed(2));
};
$("#totalDownPayment").keyup(function(){
countPay();
});
$("#assessRate").keyup(function(){
countPay();
});
$("#loanRate").keyup(function(){
countPay();
});
$("#taxRate").keyup(function(){
countPay();
});
$("#agencyFeeRate").keyup(function(){
countPay();
});
});
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>购房上车计算器</title>
</head>
<body>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>
<h1>购房首付计算器</h1>
<table>
<tr>
<td>总价</td>
<td id="total">0</td>
</tr>
<tr>
<td>贷款金额</td>
<td id="loan">0</td>
</tr>
<tr>
<td>税费</td>
<td id="tax">0</td>
</tr>
<tr>
<td>中介费</td>
<td id="agencyFee">0</td>
</tr>
<tr>
<td>净首付</td>
<td id="downPayment">0</td>
</tr>
<tr>
<td>总计首付</td>
<td><input type="text" id="totalDownPayment" value="200"></td>
</tr>
</table>
<table>
<thead>参数配置</thead>
<tr>
<td>评估系数</td>
<td><input type="text" id="assessRate" value="90">%</td>
</tr>
<tr>
<td>贷款比例</td>
<td><input type="text" id="loanRate" value="65">%</td>
</tr>
<tr>
<td>税费比例</td>
<td><input type="text" id="taxRate" value="0.95">%</td>
</tr>
<tr>
<td>中介费比</td>
<td><input type="text" id="agencyFeeRate" value="2.5">%</td>
</tr>
</table>
</body>
</html>