Is there a definitive solution to javascript floating-point errors? - Stack Overflow

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I write line of business applications. I'd like to build a front-end end using Javascript and am trying to figure out how to deal with, for a business user, are floating point errors (I understand from a puter science perspective they might not be considered errors). I've read plenty on this and seen all kinds of rounding hacks that work on examples given but seem prone to break down unexpectedly. Is there a definitive way to do decimal math in javascript?

I write line of business applications. I'd like to build a front-end end using Javascript and am trying to figure out how to deal with, for a business user, are floating point errors (I understand from a puter science perspective they might not be considered errors). I've read plenty on this and seen all kinds of rounding hacks that work on examples given but seem prone to break down unexpectedly. Is there a definitive way to do decimal math in javascript?

• javascript
• floating-point

Share Improve this question Follow edited Aug 8, 2009 at 0:39 Rex Miller 2,74611 gold badge1919 silver badges2626 bronze badges asked May 6, 2009 at 20:53 Barry GlennBarry Glenn 1

• As of June 2017, there are seven different definitive solutions – Drenai Commented Jun 9, 2017 at 14:04

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3 Answers 3

Sorted by: Reset to default 6

According to Douglas Crockford, the only way around this problem is scale your values to integer. Make sure it really is an integer by using Math.round on the scaled value. (DC does not talk about the rounding part, but I discovered it was necessary. e.g. Math.round(1.1 *100)) Do calculation(s). When you are done with the math scale back to original precision. See JavaScript: The Good Parts "Floating Point" section.

One answer is to do the math in decimal instead of binary. Then you never have to worry about the decimal <=> binary conversion errors. You'd represent the numbers as binary digits in an array or a string and write the math routines yourself.

Here are some bignumber libraries you can look into if you don't want to go to that trouble:

http://jsfromhell./classes/bignumber

http://stz-ida.de/html/oss/js_bigdecimal.html.en

the only definite solution seems to be writing your own arbitrary precision number type working on strings internally -- which will be plicated and horribly slow.

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