Convert boolean result into number/integer

Question

I have a variable that stores false or true, but I need 0 or 1 instead, respectively. How can I do this?

Answer 1

+!! allows you to apply this on a variable even when it's undefined:

+!!undefined    // 0
+!!false        // 0
+!!true         // 1

+!!()  // 1 if it evaluates to true, 0 otherwise