Question 2 From Chapter 6 Question

ommadawn · September 16th, 2005, 07:03 PM

I cannot get the code to work for question two at the end of chapter 6. Does anyone know if this does indeed work?

steenh · November 22nd, 2005, 05:09 PM

Yes - it does work (I suppose you are talking about ch6_q2.htm)

Isolator · April 16th, 2007, 03:15 PM

I copied out the example, it more or less works except the processor isn't added to the total. Can anybody see what I have missed?

<html>
<head>

<script language = JavaScript>
var CompItems = new Array();

CompItems[100] = 1000;
CompItems[101] = 1250;
CompItems[102] = 1500;

CompItems[200] = 35;
CompItems[201] = 65;
CompItems[202] = 95;

CompItems[300] = 50;
CompItems[301] = 75;
CompItems[302] = 100;

CompItems[400] = 10;
CompItems[401] = 15;
CompItems[402] = 25;

function updateOrderDetails()
{
    var total = 0;
    var orderDetails = "";
    var formElement;

    formElement =
        document.form1.cboProcessor[document.form1.cboProcessor.selectedIndex];
    total = parseFloat (CompItems[formElement.value]);
    orderDetails = "Processor : " + formElement.text;
    orderDetails = orderDetails + " $" + CompItems[formElement.value] + "\n";

    formElement =
        document.form1.cboHardDrive[document.form1.cboHardDrive.selectedIndex];
    total = parseFloat (CompItems[formElement.value]);
    orderDetails = "Hard Drive : " + formElement.text;
    orderDetails = orderDetails + " $" + CompItems[formElement.value] + "\n";

    formElement = document.form1.chkCDROM
    if (formElement.checked == true)
    {
        orderDetails = orderDetails + "CD-ROM : $" +
          CompItems[formElement.value] + "\n";
        total = total + parseFloat(CompItems[formElement.value]);
    }

    formElement = document.form1.chkDVD
    if (formElement.checked == true)
    {
        orderDetails = orderDetails + "DVD-ROM : $" +
          CompItems[formElement.value] + "\n";
        total = total + parseFloat(CompItems[formElement.value]);
    }

    formElement = document.form1.chkScanner
    if (formElement.checked == true)
    {
        orderDetails = orderDetails + "Scanner : $" +
          CompItems[formElement.value] + "\n";
        total = total + parseFloat(CompItems[formElement.value]);
    }

    formElement = document.form1.radCase
    if (formElement[0].checked == true)
    {
        orderDetails = orderDetails + "Desktop Case : $" +
          CompItems[formElement[0].value] + "\n";
        total = total + parseFloat(CompItems[formElement[0].value]);
    }
    else if (formElement[1].checked == true)
    {
        orderDetails = orderDetails + "Mini Tower Case : $" +
          CompItems[formElement[1].value] + "\n";
        total = total + parseFloat(CompItems[formElement[1].value]);
    }
    else
    {
        orderDetails = orderDetails + "Full Tower Case : $" +
          CompItems[formElement[2].value] + "\n";
        total = total + parseFloat(CompItems[formElement[2].value]);
    }

    orderDetails = orderDetails + "\n\nTotal Order Cost is $" + total;

    document.form1.txtOrder.value = orderDetails;
    }

</script>
</head>

<body>

<form name=form1>
<table>
<TR>
<TD width = 300>
Processor
<br>
<select name = cboProcessor >
    <option value = 100 >MegaPro 1ghz</option>
    <option value = 101 >MegaPro 1.2ghz</option>
    <option value = 102 >MegaPro 1.5ghz</option>

</select>
<br><br>
Hard drive
<br>
<select name = cboHardDrive >
    <option value = 200>30gb</option>
    <option value = 201>40gb</option>
    <option value = 202>60gb</option>

</select>
<br><br>
CD-ROM
<input type = "checkbox" name = chkCDROM value="300" >
<br>
DVD-ROM
<input type = "checkbox" name = chkDVD value="301" >
<br>
Scanner
<input type = "checkbox" name = chkScanner value="302" >
<br>
Desktop Case
<input type = "radio" name = radCase value="400" >
<br>
Mini Tower
<input type = "radio" name = radCase value="401" >
<br>
Full Tower
<input type = "radio" name = radCase value="402" >
<br>
<P>
<input type = "button" value = "Update" name=butUpdate onclick="updateOrderDetails()">
</P>
</TD>
<TD>
<textarea rows = 20 cols = 35 id=txtOrder name=txtOrder>

Isolator · April 16th, 2007, 04:18 PM

.................

<textarea rows = 20 cols = 35 id=txtOrder name=txtOrder>
</textarea>
</TD>
</TR>
</table>
</form>
</body>
</html>

olivaw · March 1st, 2010, 06:37 PM

Is anyone able to explain why it's necessary to use square brackets for this bit of code:

document.form1.cboProcessor[document.form1.cboProcessor.selectedIndex]

I don't understand why you can't just do formElement=document.form1.cboProcessor.selectedIn dex

Obviously if you do this it will display 'undefined'. But why is this the case?

Thanks!