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Coderslang: Become a Software Engineer

Posted on • Originally published at learn.coderslang.com on

# JavaScript Interview #13: Big numbers

We’re just logging a number, what can go wrong here?
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Under the hood, there are no integers in JavaScript.

All numbers are represented as `64-bit` floats. This is also known as `double precision`.

`52 bits` are used to store digits, `11 bits` serve to track the position of the decimal point, and `1 bit` holds the sign and determines whether the number is positive or negative.

When there’s not enough "space" to store the whole number, then rounding to the nearest possible integer occurs.

It’s impossible to store the number `9999999999999999` using `52 bits`, so the rounding gets rid of the least significant digits which leads to the result of `10000000000000000`.

In JavaScript, no error will be thrown in this case.

If you haven’t quite understood what’s going on here, make sure to read the lecture on Binary Number System of my Full Stack JS course CoderslangJS.

ANSWER: `10000000000000000` will be printed to the screen.

Learn Full Stack JavaScript

## Discussion (3)

jordanaf808

I just went through all these and learned something from each of them, thanks!

Coderslang: Become a Software Engineer

Happy to help! You can find more JavaScript interview questions with explanations here

YodaLightsabr

Yeah. Some of them were like, “Oh, I know this one!” And on others I found something really interesting to take away from it.