Manipulating binary values in JavaScript, some confusion

Question

I've got an object of values to build a bit mask from (pardon the CoffeeScript).

flags:
  segment:  1 # 00000001
  tatum:    2 # 00000010
  beat:     4 # 00000100
  bar:      8 # 00001000
  section: 16 # 00010000

And now I construct a byte in the following manner, using bitwise OR to set specific bits.

byte = 0

byte = byte | flags.segment if data.segment
byte = byte | flags.tatum   if data.tatum
byte = byte | flags.beat    if data.beat
byte = byte | flags.bar     if data.bar
byte = byte | flags.section if data.section

@sendByte(byte)

But the question is, why does this work?

I know that JavaScript stores numbers as double precision floats. Therefore, the binary representation of those number is not like a simple binary integer, right? So, does the bitwise OR | operator implicitly convert the operands somehow?

For instance, the double 4, in binary, is:

01000000 00010000 00000000 00000000 00000000 00000000 00000000 00000000

Not this value stated in my comment above:

00000100

And yet the bitwise operators work as if it was 00000010.

I do know JavaScript sure isn't afraid of implicit conversions. It just seems strange that I'm combining the bits here but those bits are entirely different than the way the values are actually stored in memory. I'm clearly missing something.

Answer 1

I'm not 100% sure about this, but it seems that bitwise operators do perform a cast to integer internally:

2 | 1
>> 3
2.6 | 1
>> 3
3 & 1
>> 1
3.2 & 1
>> 1

Edit: Seem to be confirmed by this question - using bitwise OR in javascript to convert to integer