[thelist] JS Calculator - Serious Help Needed
alex beston
alex at deltatraffic.co.uk
Wed Apr 14 11:32:45 CDT 2004
> The project is a simple
>calulator which helps clients & visitors calculate the cost of customer
>acquisition. The first thing I need to to is this: As a user selects a
>function from the drop-down list, the text 'Input 1' and 'Input 2' changes.
>
>User chooses 'Conversion Rate' and text changes to 'Number of Sales per
>Month' and 'Number of Visitors per Month'.
>
>
>
ok what you do in your .js file is to set the variable that comes in
from the form.
first you gather info and validate;
var fieldn = document.forms[0].elements[n];
(remember to include / skip hidden fields!)
eg something like:
var dropdown = document.forms[0].elements[0];
var field1 = document.forms[0].elements[1];
var field2 = document.forms[0].elements[2];
if (dropdown.value==""){
alert("choose a value");
dropdown.focus();
return false ;
}
also
if ( isNaN(field1.value) ) {
alert( "You have non numerical characters - please enter a number
" );
field1.focus();
return false ;
you go through for each form element. and if comes through you return a
true .
now you know you have usable values you can start to calculate
if (dropdown.value == "conversion rate")
// set the operator / function to use
if (dropdown.value == "cost per vistor")
// set the operator / function to use
then your function works on field1.value and field2.value and you send
the output to a text box called output / result with
document.forms[0].output.value.
so to rap up, you do this in your <head>:
<SCRIPT language="JavaScript" src="yourcode.js" type="text/javascript">
</SCRIPT>
then you call on your html a function called calculate:
<input type="button" value="Calculate" onclick="calculate();">
on the first line of the calculate function you first
if( validate()){
// do calculation
then output to the form element called ouput:
<input name="output" size="8" >
ofcourse nothing can be put into the output box until the validator is
happy.
hope that helps
rgds
Alex
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