What does the ^ (caret) symbol do in JavaScript?

It's a bitwise integer XOR operation (MDC link).

That operator performs the logical XOR operation. (out bit is 1 when both input bits are different).

The ^ operator is bitwise XOR, you have more information in MDN: https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators

It means bitwise XOR.

EDIT: Fixed link