simple shopping cart problem

Randi · Apr 2, 2004

Hi, I am trying to write this program to get this shopping cart to work. I
need to use the calc function to determine the option prices, using the
selectedIndex property for each dropdown list. This is what I have so far,
I started with if statements, but I think i need to use a for loop, because
of the array. Any help would be appreciated. The code I have so far is
below.

Thanks,

Randi

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Harmon's Computer Store</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script language="JavaScript">
var basePrice = 799;

var Ram = new Array(0, 70, 150, 280);
var HD = new Array(0, 30, 70);
var OS = new Array(0, 70, 150, 280);

function Calc(myForm){
if (myform.RAM.selectedIndex=0){
price = basePrice;
else if
(myform.RAM.selectedIndex=1){
price = basePrice + 70;}
else if
(myform.RAM.selectedIndex=2){
price = basePrice + 150;}
else if
(myform.RAM.selectedIndex=3){
price = basePrice + 280;}
}

</script>
</head>

<body>
<p align="center"><font color="#FF0000" size="+2" face="Arial, Helvetica,
sans-serif">Harmon's Computer Store</font></p>
<table width="75%" border="0">
<tr>
<td width="35%"><div align="center"><img src="images.jpg" width="103"
height="90"></div></td>
<td width="65%">The base price of this computer is $799. Because this is
a spring break
special, the manufacturer offers limited options.</td>
</tr>
</table>
<p> </p>
<p>Intel Pentium 4 300 GHz , 128 MB RAM, 40 G Hard Drive, 48x/24x/48 CD RW,
17"
color monitor.</p>
<form name="myForm" method="post" onSubmit="Calc(myForm)">
<p>Optional Upgrades</p>
<p>
<select name="RAM">
<option>128 MB</option>
<option>256 MB DDR(add $70)</option>
<option>512 MB DDR (add $150)</option>
<option>1 GM DDR (add $280)</option>
</select>
</p>
<p>
<select name="HardDrive">
<option> 40 GB</option>
<option>80 GB (add $30)</option>
<option>120 GB (add $70) </option>
</select>
</p>
<p>
<select name="OS">
<option>Windows XP Home Edition</option>
<option>Windows XP Professional Edition (add $70)</option>
<option>Windows XP Home Edition with Microsoft Plus (add $20)</option>
<option>Windows XP Home Professional Edition with Microsoft Plus (add
$90)</option>
</select>
</p>
<p>Enter your name here:
<input type="text" name="customerName">
</p>
<p>
<input type="submit" name="Submit" value="Price">
</p>
<p> </p>
</form>
<p> </p>
</body>
</html>

David Morris · Apr 2, 2004

First suggestion, change your select tags as follows:

<select name="RAM" onChange="Calc();">
<option value="0.00">128 MB</option>
<option value="70.00">256 MB DDR(add $70)</option>
<option value="150.00">512 MB DDR (add $150)</option>
<option value="280.00">1 GM DDR (add $280)</option>
</select>

This will remove the need for your arrays.

Second, add an input box somewhere as follows:

<input name=price onFocus="blur();">

Third, change your Calc() function as follows:

function Calc() {
basePrice += parseFloat(myform.RAM.value);
basePrice += parseFloat(myform.HardDrive.value);
basePrice += parseFloat(myform.OS.value);

myform.Price.value = basePrice;
}

You will probably need to format the price to pad extra zero's so $120
looks like $120.00.

Hope this helps.

David Morris · Apr 2, 2004

Oops, one error. In your function, you have to reset basePrice back to
799 or your Calc() method will grow indefinitely. See below for change....

Michael Winter · Apr 2, 2004

On Fri, 02 Apr 2004 09:56:03 -0500, David Morris

[fixed top-post]

Read the FAQ for a method of doing this:

<URL:http://jibbering.com/faq/#FAQ4_6>

[snipped OP]

Oops, one error. In your function, you have to reset basePrice back to
799 or your Calc() method will grow indefinitely. See below for
change....

Wouldn't it be a better idea to use a temporary variable during the
calculation, otherwise you start introducing "magic numbers" into the code
and increase maintenance.

function Calc() {
/* basePrice = 799; Don't do this. Use only
the original declaration */

var tmp = basePrice;

tmp += parseFloat(myform.RAM.value);
tmp += parseFloat(myform.HardDrive.value);
tmp += parseFloat(myform.OS.value);

myform.Price.value = tmp.toFixed( 2 );
}

The toFixed() call above assumes that you used the script shown in the
cited FAQ entry.

Mike

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simple shopping cart problem

Randi

David Morris

David Morris

Michael Winter

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