Finding JS max integer value in a funny way fails

Question

Today I tried to find a funny and mysterious way to determine JavaScript's maximal integer value. One of the approaches was the following:

~(+!!![]) >>> (+!![]);

which evaluates actually to

~0 >>> 1

but it returns 2147483647 and not 4294967295 as it should. Why? Of course, the latter one would be the result of this operation for an unsigned integer, while my result is correct for a signed one. But how to force it?..

One question 4294967295 is not the max intger value in Javascript. Or you were just checking max 32 bit int value. — user568109
– user568109, Commented Nov 14, 2013 at 7:24

Barmar · Accepted Answer · 2013-11-14 07:07:52Z

2

You're finding the maximum integer, and then shifting it to the right 1 bit, which divides it by 2. Use:

~0 >>> 0

to get the maximum integer.

Converting that to the "funny" way I'll leave as an exercise for the reader.

answered Nov 14, 2013 at 7:07

Barmar

789k57 gold badges554 silver badges669 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Liglo App Over a year ago

What does ">>> 0" ? Shifting by 0 bits isn't the same thing again?

Barmar Over a year ago

It is. But you have to use the >>> operator to get an unsigned result.

Liglo App Over a year ago

My approach does: 1111..1111 and than shift: 011111...111. What you do is 111111111111111 and shift nothing but delete sign bit: 0111...1111. What is the difference ? ? ?

Barmar Over a year ago

I'm not deleting the sign bit. I'm treating 1111...1111 as unsigned.

Liglo App Over a year ago

Ok, this explains it. Thank you. +1 from me. Cheers

Collectives™ on Stack Overflow

Finding JS max integer value in a funny way fails

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related