Question

I saw this piece of code in the underscore.js source:

if ((!a && b) || (a && !b)) return false;

Is that equivalent to the following?

if (a ^ b) return false;

Answer 1

Strictly speaking, no. && and || are logical operators, whereas ^ is a bit-wise operator.

But if your inputs are booleans (or integers from the set {0, 1}), then the semantics will be basically the same. If you can’t guarantee these inputs, you can still ensure identical semantics thus:

if (!a ^ !b) return false;

(Assuming, of course, that a and b are plain variables, not complex expressions with side-effects.)