Why does console.log(10150141932135203) print 10150141932135204 in both Firefox and Chrome and how to I deal with large integer values like these?

Question

I was trying to figure out why one of our clients on Facebook was having issues and I traced it to the number 10150141932135203 turning into 10150141932135204 giving us rather unexpected results.

$ node
> 10150141932135203
10150141932135204
> 10150141932135204
10150141932135204
> 10150141932135205
10150141932135204
> 10150141932135206
10150141932135206
> 10150141932135207
10150141932135208
> 10150141932135208
10150141932135208
> 10150141932135209
10150141932135208
> 10150141932135210
10150141932135210

How can I deal with integer numbers of this size?

possible duplicate of [Javascript summing large integers](http://stackoverflow.com/questions/4557509/javascript-summing-large-integers) and many, many others — mechanical_meat, Mar 06 '12 at 07:10

alex · Accepted Answer · 2012-03-06T07:14:29.773

4

If the numbers are bigger than what the IEEE 754 spec allows (2⁵³), they will lose precision as your examples demonstrate.

You could use a Binary Coded Decimal library for JavaScript, e.g. BCMathJs.

This, of course, is only applicable if you need to perform arithmetic on the numbers. If not, keep them as strings.

edited Mar 06 '12 at 07:14

answered Mar 06 '12 at 07:06

alex

479,566
201
878
984

1

That library will become crazy popular now then when every single Facebook application will be unable to reliably talk to Facebook UIDs of that size. – Kit Sunde Mar 06 '12 at 07:14
2

@KitSunde If you are not performing arithmetic, just keep them as strings. – alex Mar 06 '12 at 07:16
You also have libraries purely for integers of any size which may be faster eg https://github.com/silentmatt/javascript-biginteger – James Westgate Mar 06 '12 at 07:18
1

@alex Seems like the way to go. I also had to get HTML data attributes via `$("body").attr("data-page-id")` rather than `$("body").data("page-id")` because of this. – Kit Sunde Mar 06 '12 at 08:45
@KitSunde Yeah, the helpful *turn into a native type from guessing* sometimes isn't too helpful with `data()`. – alex Mar 06 '12 at 10:39

Why does console.log(10150141932135203) print 10150141932135204 in both Firefox and Chrome and how to I deal with large integer values like these?

1 Answers1