(I entirely agree with josh's answer: favor clear maintainable code.)
Here is an explanation on the other bit-wise approaches:
The bit-wise operators work because they only operator on 32-bit (signed) integers but numbers in JavaScript are all IEEE-754 values. Thus, there is an internal conversion (truncation, not floor!) that happens to operands for bit-wise operators.
The applied bit-wise operation (e.g. n<<0
, ~~n
or n|0
) then acts as an identity function which "does nothing" to the converted values: that is, all of these approaches rely on the same conversion applied to bit-wise operands.
Try n
as a negative number or a value outside of [-231, 231-1]:
(-1.23|0) // -1
Math.floor(-1.23) // -2
var x = Math.pow(2, 40) + .5
x|0 // 0
Math.floor(x) // 1099511627776
Happy coding.