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Question

Bug in bankersRound script

Forum|Forum|6 years ago
April 24, 2019
4 replies
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I am using this bankers rounding script as a document level script that I found online, Gaussian/Banker's Rounding in JavaScript · GitHub . It works well except it's rounding weird when working with numbers with 3+ decimal places. For example:

55.85 rounds to 55.8 (correct)

55.850 rounds to 55.8 (correct)

55.851 rounds to 55.9 (incorrect)

55.8501 rounds to 55.9 (Incorrect)

Here is the script:

function bankersRound(num,decimalPlaces){

var d = decimalPlaces || 0;

var m = Math.pow(10, d);

var n = +(d ? num * m : num).toFixed(8); // Avoid rounding errors

var i = Math.floor(n), f = n - i;

var e = 1e-8; // Allow for rounding errors in f

var r = (f > 0.5 - e && f < 0.5 + e) ?

((i % 2 == 0) ? i : i + 1) : Math.round(n);

return d ? r / m : r;

}

Any idea how this could be fixed?

Thanks so much

This topic has been closed for replies.

G

gkaiseril

Inspiring

Have you tried to respond to the source of your code.

There are a number of ways to round, Wikipedia rounding.

You need to clearly state how you expect the rounding to work and for your examples what your expected answer is.

T

Test Screen Name

Legend

Your understanding of Bankers' Rounding is different than mine, and presumably different than the author of the script. All the results you quote seem correct to me.

BarlaeDC

Community Expert

Hi,

Try67 is right this is not Acrobat specific code and I think it is rounding correctly ( as per the values, i.e. 55.851 > 55.85 and therefore rounds up) but if you round in stages then I believe you would get the answers you are looking for.

using 55.851 as the starting value.

call bankersRound ( 55.851, 2) // round to one less place than it currently has

result is 55.85

call bankersRound ( 55.85, 1)

result is 55.8 ( your expected result).

this could be done in a loop

// Replace Field names as appropriate.

var curValueToRound = this.getField("Text4").value;

// just making sure we have a string

var valueAsString = "" + initialValue;

// Assuming the number only has one decimal point in it

var numOfDigitsAfterDecimal = valueAsString.split(".")[1].length

// loop until we get to the desired decimal place ( 1)

for ( i = tempValue - 1; i >= 1; i--)

{

curValueToRound = bankersRound ( curValueToRound, i);

}

this.getField("Text8").value = curValueToRound;

Regards

Malcolm

try67

Community Expert

You should ask the people who wrote this code. This is not something PDF-specific, but a generic JS code.

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