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Why is it when I print/display the result of 

eval("11.05") + eval("-11")

it comes out as 0.05000000000000071 instead of the expected 0.05. Is there something I am missing?

T.J. Crowder
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mojothemonkey
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    This is not a `eval` issue, its due to floating point arithmetic. See [this question](http://stackoverflow.com/questions/588004/is-javascripts-math-broken) – The Scrum Meister Jun 14 '11 at 05:54

4 Answers4

5

This has nothing to do with eval. In fact, this is what happens if you type in a console 11.05 - 11: enter image description here

This is a consequence of how programming languages store floating-point numbers; they include a small error. If you want to read more about this, check this out.

Gabi Purcaru
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3

This has nothing to do with eval (which you should avoid).

You get the same problem with 11.05 - 11.

This is just the usual floating point problem

Quentin
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1

As others have indicated, this is a floating point problem and has nothing to do with eval. Now for eval: you can easy avoid it here, using:

Number("11.05") + Number("-11");

To avoid the faulty outcome you could use toPrecision:

(Number("11.05") + Number("-11")).toPrecision(12);
// or if you want 0.05 to be the outcome
(Number("11.05") + Number("-11")).toPrecision(1);
KooiInc
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0

The function eval is absolutely innocent here. The culprit is floating-point operation. If you do not expect a large number of numbers after the decimal, you may limit. But you can not avoid it.

Kangkan
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