Difference between two statements that declare an object

Question

What is the difference between this statement

var X = X || {};

And this. They do the same thing? There is a performance difference?

var X = typeof X === "undefined" ? {} : X;

Answer 1

They're not the same.

The || will return the object when X is any possible falsy value.
The typeof check will only return {} if is X is undefined.

According to this test, the undefined check is nearly twice as fast. That's probably because no type casting is required.