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
comp.lang.javascript FAQ - http://jibbering.com/faq & newsgroup weekly
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/
Coded intentionally without ; ending statements
.

Relevant Pages