javascript - Difference between two statements that declare an object -

what difference between statement

var x = x || {};

and this. same thing? there performance difference?

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

they're not same.

the || return object when x any possible falsy value.
typeof check only return {} if x undefined.

according this test, undefined check twice fast. that's because no type casting required.

Ben