Number precision in JavaScript

Question

Why 100 == 99.999 is true, however 100 == 99.99 is false in Javascript?

score 4 · Answer 1 · answered Mar 23 '11 at 07:10

4

What Every Computer Scientist Should Know About Floating Point Arithmetic

and the shorter, more to the point:

http://floating-point-gui.de/

answered Mar 23 '11 at 07:10

Marco Mariani

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score 3 · Accepted Answer · answered Mar 23 '11 at 07:07

Where are you getting that result?

From Firebug console in Firefox 3.6.3

>>> 100==99.99
false
>>> 100==99.999
false
>>> 100==99.9999
false
>>> 100==99.99999
false
>>> 100==99.999999
false
>>> 100==99.9999999
false
>>> 100==99.99999999
false
>>> 100==99.999999999
false
>>> 100==99.9999999999
false
>>> 100==99.99999999999
false
>>> 100==99.999999999999
false
>>> 100==99.9999999999999
false
>>> 100==99.99999999999999
false
>>> 100==99.999999999999999
true

@airbai, now you have two problems :) – harpo Mar 23 '11 at 07:16 — harpo, Mar 23 '11 at 07:16

score -3 · Answer 3 · answered Mar 23 '11 at 20:04

-3

Why is 100 == 99.999 true in Javascript?

It's not; whatever Javascript implementation you are using is buggy.

however 100 == 99.99 is false in Javascript?

Because they're not equal.

answered Mar 23 '11 at 20:04

Stephen Canon

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Number precision in JavaScript

3 Answers3

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