PHP, MySQL, Javascript in one big melting pot problem...

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ok, I have an order form comprising <select> boxes, populated using PHP from an SQL database...I want to use Javascript to print and refresh the total in an input box at the bottom every time a drop down box is changed...

I have this code, which doesn't work...not surpsising really...any ideas why not, or how to do this?

<script language="JavaScript">
function calc(obj)
{
var price=300.00;
for (var item=0; item < obj.elements.length; item++)
{
for (var sel=0; sel < obj.elements[item].length; sel++)
{
price = price+(eval(obj.elements[item].options[sel].value.substring((obj.elements[item].options[sel].value.length-7), 
(obj.elements[item].options[sel].value.length))));	  }
}

var cost = round2(price);
document.sys.tot.value= "Total Price £"+cost+" Inc.VAT";
window.status = "Total Price £"+cost+" Inc.VAT";
}
function round2(amount)
{
 amount = Math.round(100*amount);
 var amountstr = "" + amount;
 amountstr = amountstr.substring(0,(amountstr.length-2)) + "." + amountstr.substring((amountstr.length-2),
 amountstr.length);
 return amountstr
}
</script>

The <select> boxes are in this format:

<select name="CPUType" id="CPUType" style="width:360px" OnChange="calc(this.form)">
<?php
$result = mysql_query("SELECT prodname, sellprice FROM Products WHERE cat='CPUType' ORDER BY ourcost", $db);


while ($ra = mysql_fetch_array($result))
{

$name=$ra["prodname"];

$price=$ra["sellprice"];


echo" <option value=”$price”>$name [£$price]</option>";
}
?>
</select>

HELP...!

[ccgorman]

I think the error is here:

for(var_item=0;item<obj.elements.length;item++)
{
for(var_sel=0;sel<obj.elements[item].length;sel++)
{

Why are you going through every element on the form to do the calulation?

Also you need to get the selected index of the drop down.

Try something like this in your function:

function_calc(obj) {
var item = obj.elements['CPUType'].selectedIndex;
var choice = obj.elements['CPUType'].options[item].value;
var_price=300.00;
price=price+choice;
var_cost=round2(price);
document.sys.tot.value="Total Price £"+cost+" Inc.VAT";
window.status=_"Total Price £"+cost+" Inc.VAT";
}

Try alerts to see how far your function gets. Comment out lines and alert values, variables. If you are using Netscape you can get great feedback on errors by typing "javascript:" into the address bar.

Hope this helps

[adfinlay]

I was using every object on the form because i wanted to total the values of 18 different combo boxes...does that make any difference to the code... btw Im a complete noob to js so i have no clue...!

Any ideas...?