shorthand if/else variable exists

Question

I'm simply running a function which checks if the variable year is set if not then set it new Date().getFullYear().

The error I get:

Uncaught ReferenceError: year is not defined

year = (year) ? year : new Date().getFullYear();
console.log(year);

Why can't I check if year exists and if not set it?

Answer 1

year = year || new Date().getFullYear();

Useful to check function parameters

Answer 2

year = year ?? new Date().getFullYear();

another way