What is “x && foo()”?

Question

I saw somewhere else said,

x && foo();

　is equal to

if(x){
    foo();
}

I tested it and they really di

Answer 1

This is known as short-circuit evaluation.

In this case, if x is False, then foo() doesn't need to be evaluated (the result of && will always be False); if x is True, it does need to be evaluated (even if the result is thrown away).