Check exactly one boolean option set

Question

Well, this is kind of hacky:

function b2n(boo) {
    return boo ? 1 : 0;
}

if(b2n(opt1) + b2n(opt2) + b2n(opt3) !== 1) {
    throw new Error(\"Exactly one o         


        

Answer 1

You can do this :

if ( !!opt1 + !!opt2 + !!opt3 !== 1 ) {

It works because

• !! makes a boolean from any value (true if the objects evaluates as true in if(value))
• when adding booleans you get 1 for true and 0 for false.