Check to see if exactly two out of three booleans are true?

Question

I need to test to see if exactly two out of three booleans are true.

Something like this:

if ((a && b && !c) || (a && !b && c) || (!a && b && c)) {
  // success
}

Is this the most direct way to go about this? Does anyone know of a shortcut/shorthand?

Answer 1

To check if exactly two are equal to true:

[a, b, c].filter(Boolean).length === 2;

References:

• Array.prototype.filter().
• Boolean().

Answer 2

If you add the values you can check if the result is 2

if ((a + b + c) == 2) {
    // do something
}

Answer 3

I would go this readable (IMO) way:

let conditions = [a && b && !c, a && !b && c, !a && b && c]
if(conditions.filter(c => c).length === 2) { /* ... */}