Question

Somehow, JavaScript makes sense of the bitwise operations NaN ^ 1, Infinity ^ 1 and even 'a' ^ 1 (all evaluate to 1).

What are the rules governing bitwise operators on non numbers? Why do all the examples above evaluate to 1?

Answer 1

According to the ES5 spec, when doing bitwise operations, all operands are converted to ToInt32 (which first calls ToNumber. If the value is NaN or Infinity, it’s converted to 0).

Thus: NaN ^ 1 => 0 XOR 1 => 1