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My JavaScript Does Not Calculate Correctly

I just had some help on this script a few weeks ago and just noticed it does not calculate correctly.  It worked correctly with $100.00 input but not at $30.00 input....

You can view it here: http://billingpros.com/paypal_payment.htm

If you put a $30.00 amount in you will see it return $29.04 and it should be $28.83
<script language="JavaScript">
 
function calc(val) {
  var num = parseFloat(val.replace('$',''));
  if (isNaN(num)) return 0;
  var fee1 = (num/100)*2.9; // 2.9%
  var fee2 = (num/100)*0.30; // .30
  var newNum = num-(fee1+fee2)
  return "$"+(newNum.toFixed(2))
}
 </script>

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Asked:
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1 Solution
 
Xyptilon2Commented:
If I compute it manually, I'm also getting 29.04, why should it come out as 28.83?

0.3 * 2.9 = 0.87
0.3 * 0.3 = 0.09
Total = 0.96

30 - 0.96 = 29.04


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scrathcyboyCommented:
function calc(val) {
  var num = parseFloat(val.replace('$',''));
  if (isNaN(num)) return 0;
  num = num*100;
  var fee1 = num*29;
  var fee2 = num*3;
  var fees = fee1+fee2;
  var newNum = (num-fees)/1000;
  return "$"+(newNum.toFixed(2))

A little longer, but easy to figure out without decimals for someone not used to calculating floating points
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sh0eCommented:
30.00 - (.87 + .30) = 28.88
Why the second value should come out to .30 I don't know.  Maybe human error?
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adspaceAuthor Commented:
scrathcyboy
Have you tried that script...?
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sh0eCommented:
I get it now.  The original solution was a misunderstanding.  HE just wanted 0.30 deducted.
<script language="JavaScript">
 
function calc(val) {
  var num = parseFloat(val.replace('$',''));
  if (isNaN(num)) return 0;
  var fee1 = (num/100)*2.9; // 2.9%
  var fee2 = 0.30; // .30
  var newNum = num-(fee1+fee2)
  return "$"+(newNum.toFixed(2))
}
 </script>

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Lolly-InkCommented:
I think this is what you meant to do:
The reason why it was working for $100 is obvious now.

<script language="JavaScript">
 
function calc(val) {
  var num = parseFloat(val.replace('$',''));
  if (isNaN(num)) return 0;
  var fee1 = (num/100)*2.9; // 2.9%
  var fee2 = 0.30; // .30
  var newNum = num-(fee1+fee2)
  return "$"+(newNum.toFixed(2))
}
 
</script>

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adspaceAuthor Commented:
Xyptilon2:
No, it should be 28.83
as its  (30 cents minus 2.9 percent (thats the formula)) and it does come out to 28.83
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Xyptilon2Commented:
Then the implementation of your algorithm is not right, your script does what it is told to do and returns 29.04 (fill in the numbers as below)

var fee1 = (num/100)*2.9; // 2.9%
(30/100)*2.9 = 0.87

var fee2 = (num/100)*0.30;
(30/100)*0.30 = 0.09

var newNum = num-(fee1+fee2)
30-(0.87+0.09) = 29.04

I'm guessing Lolly-ink is right and you want to implement that algorithm like that.

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adspaceAuthor Commented:
I am trying it now
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adspaceAuthor Commented:
Lolly-Ink:
That worked fine I took a while because I had to check several inputs i.e $44.52, 188.31 etc while using a calculator and its all good

Thanks a Bunch
Sam
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adspaceAuthor Commented:
Thanks for your help
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Xyptilon2Commented:
Perhaps the next time you can rephrase your question so it more accurately describes what you want. The question you posted was not a problem in itself, the script returned the proper values. The calculations you used in the script itself were wrong, next time, please post the algorithm of what you want to accomplish so it is easier for us to understand the issue.
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