IsPowerOfTwo has bugs

[Rudxain]

JS doesn't use fixed-point int arithmetic, it uses floating-point "rationals". JS bitwise ops use "modulo" internally (specifically mod 2 ** 32), which removes all bits with an index greater than 31. So the bitwise int implementation doesn't work because IsPowerOfTwo((2 ** 53 - 1) * 2 ** 32) and IsPowerOfTwo(Infinity) return true.

I propose using trial divison by 2, since it's simple and most engines will optimize it as a simple FPFP exponent decrement. And using a "guard clause" to prevent Infinity or NaN from messing up the output:

const IsPowerOfTwo = n =>
{
  n = n?.valueOf(); //coerce to primitive, this ensures "object-wrapped" Numbers are recognized by `isFinite` method
  //technically, negative powers of 2 are valid, but this uses a narrower definiton (only unsigneds)
  if (!Number.isFinite(n) || n < 2) return false;
  //strict equality is the same as "loose" eq, when both operands are of the same type
  while (n % 2 == 0) n /= 2;
  return n == 1
}

[raklaptudirm]

If you wold like to fix this, open a pull request with the changes. Make sure to read CONTRIBUTING.md first.

[Rudxain]

Ok, thank you for the info. I'll change the code writing style to match the standard.
Edit: wait, that function is in the "bitwise" category. My implementation is correct mathematically, but the implementation shown there works fine if the input n is interpreted as a 32bit integer. What should I do? Should I add my implementation in a different directory/category?

[raklaptudirm]

If the current implementation is working, it should be left alone. You can add your implementation as a separate function with a different name, like isPowerOf2Iterative. You can use the same test cases as the other algorithm to test yours.

[Rudxain]

I think it's better to leave it as it is. Since it is in the "bit manipulation" it implicitly states that all inputs must be valid 32bit ints, so Infinity is not a valid input, which means it's okay for the return value to be wrong.
I'll close the issue, thank you for your time and help