Tuesday 26 December 2017

JavaScript adding decimal numbers issue

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Answer



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Answer






So I am making a
script that adds two numbers (decimal numbers) together, which I have encountered a
problem.




href="http://jsfiddle.net/DerekL/esqnC/"
rel="noreferrer">http://jsfiddle.net/DerekL/esqnC/



I
made the script, it turns out pretty
good:



0.1 + 0.5
//0.6
0.2 + 0.3
//0.5


But soon I
see:




0.1 + 0.2
//0.30000000000000004
0.01 + 0.06
//0.06999999999999999


And
it does not look right to me. I know it is a shortcoming of using float point with
finite bits, but I can't find a way to fix
that.



Math.ceil
//No
Math.floor //No
.slice
//No



UPDATE



Is
it possible to multiply the numbers by 1000 first, then add them then divide it by
1000?



Answer




Use toFixed to
convert it to a string with some decimal places shaved off, and then convert it back to
a number.



+(0.1 + 0.2).toFixed(12)
// 0.3



It
looks like IE's toFixed has some weird behavior, so if you need
to support IE something like this might be
better:



Math.round((0.1 + 0.2) *
1e12) / 1e12

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