» npm install decimal.js
From the Floating-Point Guide:
What can I do to avoid this problem?
That depends on what kind of calculations you’re doing.
- If you really need your results to add up exactly, especially when you work with money: use a special decimal datatype.
- If you just don’t want to see all those extra decimal places: simply format your result rounded to a fixed number of decimal places when displaying it.
- If you have no decimal datatype available, an alternative is to work with integers, e.g. do money calculations entirely in cents. But this is more work and has some drawbacks.
Note that the first point only applies if you really need specific precise decimal behaviour. Most people don't need that, they're just irritated that their programs don't work correctly with numbers like 1/10 without realizing that they wouldn't even blink at the same error if it occurred with 1/3.
If the first point really applies to you, use BigDecimal for JavaScript or DecimalJS, which actually solves the problem rather than providing an imperfect workaround.
I like Pedro Ladaria's solution and use something similar.
function strip(number) {
return (parseFloat(number).toPrecision(12));
}
Unlike Pedros solution this will round up 0.999...repeating and is accurate to plus/minus one on the least significant digit.
Note: When dealing with 32 or 64 bit floats, you should use toPrecision(7) and toPrecision(15) for best results. See this question for info as to why.
As their author, I recommend bignumber.js or big.js, 'a small, fast Javascript library for arbitrary-precision arithmetic with decimal numbers'.
For a more mature library, the ICU4J BigDecimal translation is also recommended.
There's been a "port" of the Java BigDecimal class (I think it's here: http://freshmeat.net/projects/js_bigdecimal/ ) for a long time. I looked at it a long time ago and it seemed kind-of cumbersome and huge, but (if that's the one I'm thinking of) it's been used as part of some cryptography tools so there's a decent chance that it works OK.
Because cryptography is a likely area to generate a need for such things, that's a good way to snoop around for such packages.
edit: Thanks @Daniel (comment to question) for this older SO question: https://stackoverflow.com/questions/744099/javascript-bigdecimal-library
» npm install decimal.js-light