What do the << and >> operator do? [duplicate]

问题

This question already has an answer here:

• What do these JavaScript bitwise operators do? 3 answers

I came across some code as noted below and am confused as to what it's doing.

hash += (hash << 10);

回答1:

It's a Bitwise Operator.

Here's an example from the MDN (linked to above):

     9 (base 10): 00000000000000000000000000001001 (base 2)
                  --------------------------------
9 << 2 (base 10): 00000000000000000000000000100100 (base 2) = 36 (base 10)

See how the 1s have shifted?

回答2:

This is one of the JavaScript bitwise operators:

Left Shift

a << b

Shifts a in binary representation b (< 32) bits to the left, shifting in zeros from the right.

来源：https://stackoverflow.com/questions/9606050/what-do-the-and-operator-do