JSON.Stringify() on big numbers alters the numeric value?

Question

I have a WCF service operation that returns an object with long and List<string> properties. When I test the operation in a WCF application, everything works fine and the values are correct. However, I need to be able to call the service using jQuery and JSON format. The value of the long property apparently changes when I read it back in the OnSucceed function.

After searching I've found that JSON.stringify changes big values. So in code like this:

alert(JSON.stringify(25001509088465005));

...it will show the value as 25001509088465004.

What is happening?

Demo here: http://jsfiddle.net/naveen/tPKw7/

just Test the javascript code above and see what you have send and what JSON.stringify has returned. — Amir Mohsen, Dec 27 '11 at 06:14
Due to precision limit of javascripts Number type. See also: http://stackoverflow.com/questions/588004/is-javascripts-math-broken — mbarkhau, Dec 27 '11 at 06:15
@Amir Mohsen: this has got nothing to do with JSON infact. Try this. `alert(25001509088465005);` — naveen, Dec 27 '11 at 06:17
JSON.stringify convert a JSON object in array. you can use JSON.parse instead of stringify function. check that you have return a JSON object. — Code Lღver, Dec 27 '11 at 06:23

nnnnnn · Accepted Answer · 2011-12-27T07:21:50.780

4

JavaScript represents numbers using IEEE-754 double-precision (64 bit) format. As I understand it this gives you 53 bits precision, or fifteen to sixteen decimal digits. Your number has more digits than JavaScript can cope with, so you end up with an approximation.

Do you need to do maths operations on this big number? Because if its just some kind of ID you can return it as a string and avoid the problem.

edited Dec 27 '11 at 07:21

answered Dec 27 '11 at 07:16

nnnnnn

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yeah but i wanted to have it as long but finally I receive it as string and this is the end of that. – Amir Mohsen Dec 27 '11 at 07:33
There is no "long" datatype in JavaScript, only Number. – Anders Marzi Tornblad Dec 27 '11 at 07:57
Yes, I should have explicitly said "JavaScript represents _all_ numbers using..." – nnnnnn Dec 27 '11 at 08:11
at last I used string instead of that 17 digits number and life is beautiful now – Amir Mohsen Dec 28 '11 at 13:13

JSON.Stringify() on big numbers alters the numeric value?

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