Checking Function inside IF statement explanation

I'm declaring a function which is used as a comparison. My question is:

Why does the condition act as a statement?

why does line 4 work but not line 5?

I know this code is unrealistic and unused, but why does the compiler allow this syntax?

There is no answer on google. But then again, I might have not look in the right place.

var A = () => console.log(3);

if (A === console.log(1)) {
  A();
};

A ? A() : null;

if (A === console.log(1567)) {};

if (B === console.log(1567)) {};

The expected output is:

3

The output is:

1

3

1567

Uncaught ReferenceError: B is not defined at :11:1