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javascriptfloating-pointdoublefloating-accuracynumerical-methods

Dealing with float precision in Javascript

I have a large amount of numeric values y in javascript. I want to group them by rounding them down to the nearest multiple of x and convert the result to a string.

How do I get around the annoying floating point precision?

For example:

0.2 + 0.4 = 0.6000000000000001

Two things I have tried:

>>> y = 1.23456789 
>>> x = 0.2 
>>> parseInt(Math.round(Math.floor(y/x))) * x; 
1.2000000000000002

and:

>>> y = 1.23456789 
>>> x = 0.2 
>>> y - (y % x)
1.2000000000000002
Solution

  • From this post: How to deal with floating point number precision in JavaScript?

    You have a few options:

    • Use a special datatype for decimals, like decimal.js
    • Format your result to some fixed number of significant digits, like this:

    (Math.floor(y/x) * x).toFixed(2)

    • Convert all your numbers to integers