help on the select box calcualtion

wangtian · April 6, 2011

any one can help me on this code? the problem on this code is that it only give me the result of the last mutification (chassis.value * Quantity1.value). I want to get the result of motherboard.value * Quantity + Chassis.value * quantity1. anyone know how to fix this problem. I appreciate it.

function calculate(){
document.calcform.total.value = parseFloat(document.calcform.Motherboard.value || 0) * parseFloat(document.calcform.Quantity.value || 0)
+ parseFloat(document.calcform.Chassis.value || 0) * parseFloat(document.calcform.Quantity1.value || 0) }

here are the code on my page.

<style type = "text/css">

.SelectClass { 
  font-size: 15px; 
} 

table {

font-size: .9em;
border: 3px groove;
padding: 0px;
background-color: #dddddd;
}

.mycss
{
font-weight:normal;font-style:italic;color:#000000;letter-spacing:1pt;word-spacing:2pt;font-size:36px;text-align:left;font-family:courier new, courier, monospace;line-height:1;
}


</style>





<script LANGUAGE="JavaScript">

function dp(price)
{
string = "" + price;
number = string.length - string.indexOf('.');
if (string.indexOf('.') == -1)
return string + '.00';
if (number == 1)
return string + '00';
if (number == 2)
return string + '0';
if (number > 3)
return string.substring(0,string.length-number+3);
return string;
}

function calculate(){
document.calcform.total.value =dp(parseFloat(document.calcform.Motherboard.value|| 1)* parseFloat(document.calcform.Quantity.value || 1)+parseFloat(document.calcform.Chassis.value|| 0)* parseFloat(document.calcform.Quantity1.value || 0)) } 
</script>


</head>

<body onload="calculate">
<div class="mycss"><center>Order List</center></div><br />

<center>
<form name="calcform"  method="post" action="test2.php">

<table border="0"  width="800">

<tr>
<td align="right" colspan="2">

<font size="6">$</font><input name="total" style="border:0px solid #000000; background-color:#E6FBF4; font-size: 25.5px;"  type="text" value="0.00" ONCHANGE="calculate()"/> 

</td></tr>


<tr>
<td><font size="+1">
Product Name</font>
</td>

<td><font size="+1">Quantity</font></td></tr>
<td colspan="2">
<?php
mysql_connect("mysql1.000webhost.com", "a4202648_wang", "wang2011") or die(mysql_error());

mysql_select_db("a4202648_wang") or die(mysql_error());

echo "<table  width='100%'>";


echo "<tr><td align='left' width='90%'>";

$result = mysql_query("SELECT Motherboard_Part_Number, Motherboard_Name, Motherboard_Price FROM Motherboard ") 
or die(mysql_error());  
echo '<select id="Motherboard" class="SelectClass" name="Motherboard" ONCHANGE="calculate()">'; 
// keeps getting the next row until there are no more to get
while($row = mysql_fetch_array( $result )) {
// Print out the contents of each row into a table
echo '<option Name="Motherboard" value= ',$row['Motherboard_Price'],'>',$row['Motherboard_Part_Number'],'   ',$row['Motherboard_Name'],'    $',$row['Motherboard_Price'],' ','</option>'; 

} 

echo '</select>';

echo "</td>";


echo "<td align='right' width='10%'>";

$result= mysql_query("SELECT Number FROM Quantity") 
or die(mysql_error());  
echo '<select id="Quantity" class="SelectClass" name="Quantity" Value="Quantity" ONCHANGE="calculate()" >'; 

// keeps getting the next row until there are no more to get
while($row = mysql_fetch_array( $result)) {
// Print out the contents of each row into a table

echo '<option value=',$row['Number'],'>',$row['Number'],'</option>'; 
} 




echo '</select>';

echo "</td></tr>";











echo "<tr><td align='left' width='90%'>";

$result = mysql_query("SELECT Chassis_Part_Number, Chassis_Name, Chassis_Price FROM Chassis where Chassis_Form_Factor='ATX'") 
or die(mysql_error());  
echo '<select id="Chassis" class="SelectClass" name="Chassis" ONCHANGE="calculate()">'; 
// keeps getting the next row until there are no more to get
while($row = mysql_fetch_array( $result )) {
// Print out the contents of each row into a table
echo '<option Name="Chassis" value= ',$row['Chassis_Price'],'>',$row['Chassis_Part_Number'],'   ',$row['Chassis_Name'],'    $',$row['Chassis_Price'],' ','</option>'; 

} 

echo '</select>';

echo "</td>";


echo "<td align='right' width='10%'>";

$result= mysql_query("SELECT Number FROM Quantity") 
or die(mysql_error());  
echo '<select id="Quantity" class="SelectClass" name="Quantity1" Value="Quantity" ONCHANGE="calculate()" >'; 

// keeps getting the next row until there are no more to get
while($row = mysql_fetch_array( $result)) {
// Print out the contents of each row into a table

echo '<option value=',$row['Number'],'>',$row['Number'],'</option>'; 
} 




echo '</select>';

echo "</td></tr>";









echo "</table>";
?>
</td>
</tr>
<tr><td colspan="2"><input type="submit" /></td></tr>
</table>

</form>
</center>

</body>
</html>

[attachment deleted by admin]

Adam · April 7, 2011

Although you haven't actually said what the problem is, I imagine it's down to the order of operations. You need to use parentheses () to group the calculations, so that you first work out (Motherboard * Quantity), then (Chassis * Quantity), and then add the two. To make things a little more readable you can also store document.calcForm as a variable...

function calculate() {
    var calcForm = document.calcForm;
    calcForm.total.value =
          (parseFloat(calcForm.Motherboard.value || 0) * parseFloat(calcForm.Quantity.value || 0))
        + (parseFloat(calcForm.Chassis.value || 0) * parseFloat(calcForm.Quantity1.value || 0))
}

Notice the additional brackets.

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help on the select box calcualtion

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