What does >>= mean in JavaScript?

Question

I found this in the dojo.js library:

13444: color >>= bits;

Context:

ArrayUtil.forEach(["b", "g", "r"], function(x){
  var c = color & mask;
  color >>= bits;
  t[x] = bits == 4 ? 17 * c : c;
});

I can't find any reference to it anywhere else. It's not in the O'Reilly JavaScript pocket reference or the Wikipedia page.

I know what it means in functional programming, but I'm pretty sure JavaScript doesn't support monads!

Answer 1

It is the same a color = color >> bits - similar to operators like +=, -=, *= ...

EDIT

The >> (in the integer context) shifts bits to the right, i.e. dividing by 2 but keeping the sign bit in the same place

Answer 2

It is Right Shift operator. For example, the a >> b operator is actually same as a/2^b.

In your case, it is equal to: color = color >> bits where color >> bits stands for color/2^bits

As you can see, it divides first operand with 2 raised power of second operand eg 2^bits; whatever is the value of bits there.

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You can read more about it at MDN.