[removed] || instead of IF statement - is this legal and cross browser valid?

Question

It seems that:

if (typeof a == \'undefined\') {
    a = 0;
}

and

(typeof a != \'undefined\') || (a = 0)

h

Answer 1

Moreover I suppose it would impact performances because

(typeof a != 'undefined') || (a = 0)

is composed of two test (even if we don't care about the second one).

Whereas

if (typeof a == 'undefined') {
    a = 0;
}

contains only one test