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Thread: mortgage calculator problems

  1. #1
    Join Date
    Aug 2006

    mortgage calculator problems

    Hi all,

    I am trying to modify a mortgage calculator script that I found at: http://www.1stop-mortgagecalculator....culator-Script.

    I'm new to js and I need my result "monthly_payment" to display on the form in a text box. Can anyone tell me how to do it? A colleague suggested to put it in a div tag and use .InnerHtml, however, I don't know how to do that and I am unfamiliar with the .innerHtml property(?)

    Here is my code:

    <meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
    <title>Mortgage calculator</title>


    <script language="JavaScript" type="text/javascript">

    function find_payment(PR, IN, PE) {
    var PAY = (PR * IN) / (1 - Math.pow(1 + IN, -PE))
    return PAY

    //var principal = 200000
    //var interest = 0.088
    //var term = 30
    //var monthly_payment = find_payment(principal, interest / 12, term * 12);

    var principal = document.formpage.principal.value;
    var interest = document.formpage.interest.value/100;
    var term = document.getElementById('years').term.value;
    var monthly_payment = find_payment(principal, interest / 12, term * 12);

    //document.write("Amount of the loan: $" + principal + "<br>" +
    //"Annual interest rate:\t" + interest * 100 + "%<br>" +
    //"Term of the mortgage loan:\t" + term + " years<br><br>" +
    //"Monthly payment: $" + monthly_payment)

    //alert("Amount of the loan:\t$" + principal + "\n" +
    //"Annual interest rate:\t" + interest * 100 + "%\n" +
    //"Term of the mortgage loan:\t" + term + " years\n\n" +
    //"Monthly payment:\t$" + monthly_payment)


    <form name="formpage">
    <table bgcolor="#ffffff" border="0" cellpadding="0" cellspacing="0" width="478">
    <tr valign="top">
    <td width="183">Amount to be financed:<br /></td>
    <td width="183"><input name="principal" size="7" maxlength="12" type="text"><br /><br /></td>

    <tr valign="top">
    <td>Current fixed rate:&nbsp; <br /><br /></td>
    <td>8.80%*<input name="interest" size="5" value="8.80" type="hidden"><br /><br /></td>

    <tr valign="top">
    <td>Years financed:&nbsp; <br /><br /></td>
    <td><select name="term" id="years">
    <option value=""></option>
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
    <option value="4">4</option>
    <option value="5">5</option>
    <option value="6">6</option>
    <option value="7" selected="selected">7</option>
    <option value="8">8</option>
    <option value="9">9</option>
    <option value="10">10</option>
    </select><br /><br /></td>

    <tr valign="top">
    <td colspan="2" height="39">
    <input src="images/btn_calculate.gif" onclick="find_payment(PR, IN, PE)" alt="calculate payment" type="image" width="83" height="16">
    <img src="images/spacer.gif" border="0" height="16" width="3">
    <a href="jstest.htm"><img src="images/btn_clear.gif" alt="close window" border="0" height="16" width="59"></a> <br />

    <tr valign="top">
    <td colspan="2" class="footnote">
    <p> * Valid as of June 1, 2006
    <input name="txtDate_Last_Updated" size="5" value="2/1/2006" type="hidden">
    </p> </td>




    I keep getting an error: "document.formpage.principal is null or not an object". I am very confused. Can any one help me out?

    THANKS, I appreciate it!!!

  2. #2
    Join Date
    Nov 2002
    Flint, Michigan, USA
    Add a field to hold the output:
      <input type="text" id="result">
    In the script in place of the document.write, put in code to display the result in the above field:

  3. #3
    Join Date
    Aug 2006
    Thanks very much jalarie. I didn't know anyone replied. I'll post the solution I used as soon as I find it.

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