In JS, we have the following situation:
<< operator:
3 << 1 // 6
5 << 1 // 10
7 << 1 // 14
-3 << 1 // -6
-5 << 1 // -10
-7 << 1 // -14
>> operator:
3 >> 1 // 1
5 >> 1 // 2
7 >> 1 // 3
-3 >> 1 // -2
-5 >> 1 // -3
-7 >> 1 // -4
As you can see, for the << operator, and for values less than 2**32, we have abs(X << Y) === abs(-X << Y).
Why doesn't this keep true for the >> operator?
Because you are rotating the binary representation of those numbers. And the negative numbers are stored as 2's complement binary
So (using just 8-bits for illustration purposes):
-3 = 11111101
Which if you rotate with >> which is sign propagating you will get:
11111110 = -2
Because the sign propagating shift copies the sign bit to the left-most bit.
With the positive numbers it's easier:
3 = 00000011
After shifting with >> (since it's positive, you are shifting in zeros)
00000001 = 1
It's because minus has greater precedence than shift operator.
So, -3 >> 1 will run as (-3) >> (1) but not as -(3 >> 1).