Re: Simple totalling of a column with onChange()

charliefortune said the following on 4/29/2006 2:20 PM:
> Every time a field in an accounts form changes, an onChange =
> "updateAmount()" executes this function -
>
> function updateAmount(x){
> var field = 'amount' + x;
> var val = parseFloat(document.forms[0].field.value);

var val = +document.forms[0].elements['amount'+x].value;

> document.forms[0].totAmount.value = val;
> }
>
> the fields are called 'amount1', 'amount2', 'amount3' etc. and the
> onChange passes that integer. I want to calculate a new total every
> time a new amount is entered.

Don't pass the integer, pass a reference to the field itself using the
'this' operator. But, for what you are doing, you don't need a reference
to the element at all.

Do a test:

Fill out the form, go back and change the first input to a new number,
your results will be wrong.

> 1. Is there a way to avoid having to pass the 'x' index. Surely the DOM
> knows which field is provoking the function call.

It doesn't matter in this case, you need to re-total all the fields
every time one changes.

> 2. The parseFloat doesn't seem to work, is my syntax correct ?

No.

Try this:

function getTotal(){
formRef = document.forms[0]
var totalFields = formRef.elements.length
var totalCounter = 0
for (var i=0;i<totalFields;i++)
   {
   if (formRef.elements[i].name.indexOf('amount') == 0)
     {
     totalCounter += +formRef.elements[i].value
     }
   }
formRef.elements['totAmount'].value = totalCounter
}

It depends on any field being calculated starting with the string "amount".

-- 
Randy
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