Looking for help with this nested ternary operator.

Question

Hi, I just can't wrap my head around this one challenge question from JavaScript.

function f(a) {
return a > 0 ? 0 && 1 ? 1 : 0 : 1;
}
console.log(f(0)); //Output: 1
console.log(f(1)); //Output: 0
console.log(f(2)); //Output: 0

Can someone explain what is happening here?

Answer 1

For me it always helps splitting the view in outer and inner part. The outer part is easy:
if a > 0 do inner part else return 1.
Now the inner part:
if 0 && 1 do return 1 else return 0.
However, 0 && 1 is always false, so whenever this is executed, 0 will be returned.

As to the function calls:
In the first call, the outer condition is false, therefore 1 is returned.
For the other calls, the outer part evaluates to true, the inner part is executed, which returns 0 anyway, therefore they print 0.

Answer 2

Thanks, Naitomea.
Now this seems rather clear. Basically I can just wrap inner part into parentheses.

function f(a) {
return a > 0 ? ((0 && 1) ? 1 : 0) : 1;
}

At first I somehow assumed && meant double check like a > 0 and a > 1, but it was just (false && true) condition.

Answer 3

Yes, wrapping the inner part into parentheses is a good idea because it aids the readability. I've done that a lot lately.