Does JavaScript Number.toString method lose accuracy after a threshold?

Question

The output of the following:

let x = 10**23;
console.log(x.toString(16))

comes out 152d02c7e14af6000000 which actually computes to 99999999999999991611392 and not 10**23. Interestingly enough, the following doesn't compute to false:

let x = 10**23;
console.log(x==parseInt(x.toString(16),16))

Am I getting something wrong here?

Javascript maximum safe integer is 2^53-1, which is lower than 10^23. — N.F., Aug 17 '22 at 06:14
@Justinas yes, using BigInt gives me the correct hex representation — Parth Mall, Aug 17 '22 at 06:21

gustafc · Accepted Answer · 2022-08-17T06:19:35.380

3

JavaScript numbers are floating point, which lose precision the larger they get. When you exceed Number.MAX_SAFE_INTEGER (which is 2⁵³ – 1), the precision becomes >1.

This also means that things like 10**23 === (1**23 - 123) evaluates to true.

edited Aug 17 '22 at 06:19

answered Aug 17 '22 at 06:14

gustafc

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Does JavaScript Number.toString method lose accuracy after a threshold?

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