simplify formatNumber logic

[millermedeiros]

no need to check if number is negative or do multiple substr.. A single RegExp is enough, check my implementation: http://stackoverflow.com/questions/149055/how-can-i-format-numbers-as-money-in-javascript/3284302#3284302

[wjcrowcroft]

Thanks, will take a look at it and reply in a bit!

[wjcrowcroft]

I've taken a look at the stackoverflow answer and played around with the function and regex you suggest - I'm getting this issue for large numbers though, which maybe you can help out with:

numberToCurrency(1234567890.99)  // "1,234,567,890.99"
numberToCurrency(123456789012345678.99)  // "123,456,789,012,345,680.00"
numberToCurrency(12345678901234567890.99)  // "12,345,678,901,234,567,168.00"

Looks like it's losing some info off the end of the number, after a certain number of digits. Any ideas why?

Otherwise, it seems good and slightly better optimised, so if we can make sure there are no hidden issues with it, I'm happy to try incorporating it.

[millermedeiros]

This happens because of 64-bit floating point Numbers. The maximum integer you can have without loosing precision is Math.pow(2, 53) == 9007199254740992 even tho Number.MAX_VALUE is way higher than that (same happens for negative numbers).

This bug can be replicated by:

console.log(Math.pow(2, 53) == (Math.pow(2, 53) + 1)); // true

Another thing that is good to note is that some operators only accepts integers until Math.pow(2, 31) - 1 == 2147483647 (positive or negative - if they deal with Int values - like bitwise operations)... if operator deals only with unsigned ints it works from 0 till Math.pow(2, 32).

[wjcrowcroft]

Great explanation, thanks. If that's the only issue and it's language-level (similar to how (0.615).toFixed(2) === "0.61") I don't see an issue with trying to implement this regex into the number formatting - I'll have a play around tomorrow and see what works.

Cheers!

[wjcrowcroft]

FYI - there are a few issues with the function you posted on StackOverflow:

precision of 0 is always forced to 2 by nDecimalDigits = nDecimalDigits || 2;, so that:

numberToCurrency(12345, '.', ',', 0) // "12,345.00"

If I replace that nDecimalDigits with nDecimalDigits = !nDecimalDigits ? "." : nDecimalDigits; (check for undefined as opposed to 0), the regex fails, so no thousand separators are inserted:

numberToCurrency(12345, '.', ',', 0) // "12345"
numberToCurrency(12345, '.', ',', 1) // "12,345.0"

I checked out the regular expression and looks like it can't handle numbers without decimal places. I'm not amazing at regexes though, so if you could suggest a fix for that, I'll be happy to include it in the library with attribution :)

Any ideas? thanks!