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javascript - math leaving off a digit

Posted on 2009-06-30
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Last Modified: 2012-05-07
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  
      {
            alert ('Please enter a number.  No commas or letters.');
            }
}
 
 
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#">

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Question by:wkolasa
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Author Comment

by:wkolasa
ID: 24746921
The issue is in the function calc()
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Author Comment

by:wkolasa
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
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Author Comment

by:wkolasa
ID: 24747115
parseInt  is not digging the onKeyPress   but even knowing that I don't have a solution yet
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LVL 41

Expert Comment

by:HonorGod
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);

    Use this instead:

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

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

by:wkolasa
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).
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Author Comment

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

by:Xxavier
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

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LVL 7

Accepted Solution

by:
Xxavier earned 500 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)){ 
             alert ('Please enter a number.  No commas or letters.');
             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>

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Author Closing Comment

by:wkolasa
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!
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