Javascript issue with math calculations

Question

Why is it if I do this in javascript, I get the following result:

1234.56 * 10 = 12345.599999999999

It should be 123456. How can I get around this problem?

Thanks.

Not exactly sure what you mean by "doing it with jQuery". jQuery is a DOM manipulation extension, not a math library. Can you please post a code sample? — Traveling Tech Guy, Oct 16 '11 at 21:51
Also, it would be 12345.6 - you'd have to multiply by 100 to get 123456. — methodin, Oct 16 '11 at 21:54
See http://stackoverflow.com/questions/588004/is-javascripts-math-broken — Chris, Oct 16 '11 at 21:54

mzalazar · Answer 1 · 2015-03-04T11:28:53.807

3

Another easy solution:

parseFloat((1234.56 * 10).toPrecision(12))

and the result will be: 12345.6, and YES... it works with decimal numbers.

edited Mar 04 '15 at 11:28

answered Jan 15 '15 at 21:09

mzalazar

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score 3 · Answer 2 · answered Oct 16 '11 at 21:52

3

Floating points are not exact, since there are ifinite numbers at their range [or in any range to be more exact], and only a finite number of bits to store this data.

Have a look at what every programmer should know about floating point arithmetics.

answered Oct 16 '11 at 21:52

amit

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adeneo · Answer 3 · 2011-10-16T22:58:54.257

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As the others said, floating points and so on.

Easy solution would be to do something like this:

var answer = parseInt(1234.56 * 10);

Or just use Math.round?

edited Oct 16 '11 at 22:58

answered Oct 16 '11 at 22:28

adeneo

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score 0 · Answer 4 · answered Oct 16 '11 at 21:59

All numbers in JS are internally defined by float and drop the less significant digits if needed.

(10000000000000000000000000000 + 1) == 10000000000000000000000000000
// this will return true

And javascript is well known for droping bits quite often in numbers. So handle with care

Javascript issue with math calculations

4 Answers4