Question

In lamens terms, what does a bitwise | operator do in Javascript and why is:

8 | 1 ; //9

Answer 1

8 in binary = 1000
1 in binary = 0001

if you take each binary digit and treat them as if statements (1 being true and 0 being false), you get this:

1 || 0 = 1
0 || 0 = 0
0 || 0 = 0
0 || 1 = 1

and the result is 1001, which is 9 in decimal

If it had been 8 & 1, it would go like this:

1 && 0 = 0
0 && 0 = 0
0 && 0 = 0
0 && 1 = 0

and the result would be 0

Here’s a quick example of how you might use these:

You would use the OR operator if you wanted to combine masks –

Using an example of file permissions, you may have the following flags:

1st bit - execute (bin - 001, dec - 1)
2nd bit - write (bin - 010, dec - 2)
3rd bit - read (bin - 100, dec - 4)

If you wanted to create a mask for read and execute, you’d do something like read value | execute value which is 1 | 4 which would give you 5 (101 in bin)

Now you have a mask that you can check a file’s permissions to see if it has both of these permissions, using the & operator:

Example file 1 (has read, write, and execute)

Its permission value is 7 (111 in bin): 111 & 101 = 101, so it does have those perms

Example file 2 (has read and write)

Its permission value is 6 (110 in bin): 110 & 101 = 100, so it only has the 100 (4 in dec) perms (read) of the two provided from the mask