此外，我还意识到单击“计算”之前键入的值也消失了。直到现在我仍然找不到错误，因为我认为我计算抵押贷款的公式是正确的。
HTML代码：
<html>
<head>
<script src="cal_mortgage.js" type="text/javascript"></script>
</head>
<body>
<form>
<table>
<h2>mortgage calculator:</h2>
<tr><td>principal</td><td><input type="text" id="principal"/></td></tr>
<tr><td>interest %</td><td><input type="text" id="interest"/></td></tr>
<tr><td>term (year)</td><td><input type="text" id="term"/></td></tr><p></p>
<tr><td><input type="submit" value="calculate" onclick="cal_mortgage()"/></td><td></td></tr>
<tr><td>monthly payment</td><td><input type="text" id="monthly_pay"/></td></tr>
</table>
</form>
</body>
</html>
JavaScript代码：
function cal_mortgage()
{
var PR = form.principal.value; /*present value of the mortgage loan*/
var IN = (form.interest.value / 100) / 12; /*interest rate of the mortgage loan*/
var PE = form.term.value * 12; /*number of periods of the mortgage loan*/
var PAY = (PR * IN) / (1 - Math.pow(1 + IN, -PE)); /*regular payment to apply to the mortgage loan*/
form.monthly_pay.value = PAY;
}
在您的html文件中，更改<form>为<form id="Calculate">并将按钮类型从提交更改为按钮
在您的javascript cal_mortgage（）函数中，将其添加为第一行：
form = document.getElementById("Calculate")
现在应该可以了
新代码：
function cal_mortgage()
{
form = document.getElementById('Calculate')
var PR = form.principal.value; /*present value of the mortgage loan*/
var IN = (form.interest.value / 100) / 12; /*interest rate of the mortgage loan*/
var PE = form.term.value * 12; /*number of periods of the mortgage loan*/
var PAY = (PR * IN) / (1 - Math.pow(1 + IN, -PE)); /*regular payment to apply to the mortgage loan*/
form.monthly_pay.value = PAY;
}
<html>
<head>
<script src="cal_mortgage.js" type="text/javascript"></script>
</head>
<body>
<form id="Calculate">
<table>
<h2>mortgage calculator:</h2>
<tr><td>principal</td><td><input type="text" id="principal"/></td></tr>
<tr><td>interest %</td><td><input type="text" id="interest"/></td></tr>
<tr><td>term (year)</td><td><input type="text" id="term"/></td></tr><p></p>
<tr><td><input type="button" value="calculate" onclick="cal_mortgage()"/></td><td></td></tr>
<tr><td>monthly payment</td><td><input type="text" id="monthly_pay"/></td></tr>
</table>
</form>
</body>
</html>
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我来说两句