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# javascript - math leaving off a digit

Posted on 2009-06-30
Medium Priority
284 Views
Hi,

I have a javascript that converts numbers to decimals (adds decimals if needed and does simple math).  It uses three fields to autoFill the 4th.  Field 1 is addition.  Field 2 subtraction.  Field 3 addition.  Field 4 should reflect the calculation of 1,2,3.  The problem is this.  If I type 20 into field 1, field four shows 2.00... and NOT 20.00.  This si probably a simple fix, and this was working great when I was using onChange instead of onKeyPress.

Code is below.  Thank you very very much ... Wendi~
``````<script type="text/javascript">

function calc(){
one = document.autoSumForm16.budget_income1.value;
two = document.autoSumForm16.budget_income2.value;
three = document.autoSumForm16.budget_income3.value;
if (one >'' && two > '' && three > '' ) {
var sum  = parseInt(one) - parseInt(two) + parseInt(three);

var num = new NumberFormat(sum).toFormatted();
document.autoSumForm16.budget_income4.value = num;
document.autoSumForm16.budget_exp4.value = num;
}
else
{
}
}

function CurrencyFormatted(amount)
{
var i = parseFloat(amount);
if(isNaN(i)) { i = 0.00; }
var minus = '';
if(i < 0) { minus = '-'; }
i = Math.abs(i);
i = parseInt((i + .005) * 100);
i = i / 100;
s = new String(i);
if(s.indexOf('.') < 0) { s += '.00'; }
if(s.indexOf('.') == (s.length - 2)) { s += '0'; }
s = minus + s;
return s;
}

</script>

<!--- These three fields calc the one below.  I want it to be where simply typing being the calculation, and instantly changes
the number below --->
<input type="Text"  name="budget_income1" style="text-align:right;" onKeyPress="calc();" value="0">
<input type="Text"  name="budget_income2" style="text-align:right;" onKeyPress="calc();" value="0">
<input type="Text"  name="budget_income3" style="text-align:right;" onKeyPress="calc();" value="0">

<!--- This is the field being calculated by the 3 above --->
<input type="Text"  name="budget_income4"  style="text-align:right;" value="#getform.budget_income4#">
``````
0
Question by:wkolasa
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Author Comment

ID: 24746921
The issue is in the function calc()
0

Author Comment

ID: 24746969
The issue, which i haven't solved, is this.  Because of the onKeyPress instead of onChange, javascript doesn't know/care about decimals from the first three inputs.  In other words... if in the first field I type 10.00, field 4 = 10.00.  But if in the first field I type 1,   field 4 = 0.00
0

Author Comment

ID: 24747115
parseInt  is not digging the onKeyPress   but even knowing that I don't have a solution yet
0

LVL 41

Expert Comment

ID: 24747269
1. You don't want to be calling calc when a key is pressed.  This is a really bad idea...

2. To check for non-empty fields, change your if expression from this:

if (one >'' && two > '' && three > '' ) {

to this:

if (one && two && three ) {

3. When you use parseInt(), be sure to include/specify the radix.  So, instead of using

var sum  = parseInt(one) - parseInt(two) + parseInt(three);

var sum  = parseInt( one, 10 ) - parseInt( two, 10 ) + parseInt( three, 10 );
0

Author Comment

ID: 24747277
Excellent.  Thank you.  I Know, beleive me I know this is a bad idea.  The client is demanding it.
0

Author Comment

ID: 24747312
I set the function as you outlined.  I'm still having the same problem though.  I tried to add decimals using toFixed... no good (probably a dumb idea, but I pretty new with javaScript).
0

Author Comment

ID: 24747349
The function simply doesn't see the first digit of the onKeyPress event
0

LVL 7

Expert Comment

ID: 24747418
Looking at this I think you have made a simple problem very complicated. There are a number of easy ways of converting to numbers to  do arithmetic.  I can not test your code as it is incomplete., however

(1) Multiply a string by 1.0 converts it to a number
(2) num.toFixed(2) ouputs num to 2 decimal places
(3) isNaN(num) checks if num is a number

0

LVL 7

Accepted Solution

Xxavier earned 2000 total points
ID: 24747553
also you need onKeyUp()  no  onKeyPress()

try this
``````<script type="text/javascript">

function calc(){
one = 1*document.autoSumForm16.budget_income1.value;
two = 1*document.autoSumForm16.budget_income2.value;
three = 1*document.autoSumForm16.budget_income3.value;
if (isNaN(one)|isNaN(two)|isNaN(three)){
return
}
var num = one - two + three;
document.autoSumForm16.budget_income4.value = num.toFixed(2);
}

</script>

<form name=autoSumForm16>
<input type="Text"  name="budget_income1" style="text-align:right;" onKeyUp="calc();" value="0">
<input type="Text"  name="budget_income2" style="text-align:right;" onKeyUp="calc();" value="0">
<input type="Text"  name="budget_income3" style="text-align:right;" onKeyUp="calc();" value="0">

<!--- This is the field being calculated by the 3 above --->
<input type="Text"  name="budget_income4"  style="text-align:right;" value=""> </form>
``````
0

Author Closing Comment

ID: 31598397
You're right, it is overly complicated.  Can't be helped.  Much of the code,  convoluted structure is already in place.

Thank you very much!
0

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