How to fix 0.3+0.6=0.89999999999 in Javascript?

Question

When adding two float values, I will get something like:

0.3+0.6 = 0.89999999999

I know what's going on. In C# we can use decimal instead, but in Javascript, how to fix it?

If it is just a presentation problem, use `.toFixed` to format the floating point number as a string. — Douglas, Aug 05 '14 at 09:43
http://stackoverflow.com/questions/588004/is-floating-point-math-broken — meo, Aug 05 '14 at 09:47

score 2 · Accepted Answer · answered Aug 05 '14 at 09:52

2

MathUtils

MathUtils = {
    roundToPrecision: function(subject, precision) {
        return +((+subject).toFixed(precision));
    }
};

console.log(MathUtils.roundToPrecision(0.3 + 0.6, 1)) // 0.9;

answered Aug 05 '14 at 09:52

Krzysztof Safjanowski

7,292
3
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score 0 · Answer 2 · answered Aug 05 '14 at 09:40

0

Essentially the same way, but JavaScript doesn't have a decimal-like number type built in. If you search, you can find various implementations like big.js (just an example, not a recommendation).

answered Aug 05 '14 at 09:40

T.J. Crowder

1,031,962
187
1,923
1,875

score 0 · Answer 3 · answered Aug 05 '14 at 09:43

Use a BigNumber library. For example math.js has support for bignumbers (powered by decimal.js).

Using the expression parser of math.js, you can type natural expressions using bignumbers:

// configure math.js to use bignumbers
math.config({number: 'bignumber'});

// evaluate an expression
math.eval('0.3 + 0.6'); // returns a BigNumber with value 0.9

How to fix 0.3+0.6=0.89999999999 in Javascript?

3 Answers3

MathUtils