The nullish coalescing proposal (??) adds a new short-circuiting operator meant to handle default values.
The nullish coalescing operator (??) acts very similar to the || operator, except that we don’t use “truthy” when evaluating the operator. Instead we use the definition of “nullish”, meaning “is the value strictly equal to null or undefined”. So imagine the expression lhs ?? rhs: if lhs is not nullish, it evaluates to lhs. Otherwise, it evaluates to rhs.
false ?? true; // => false
0 ?? 1; // => 0
'' ?? 'default'; // => ''
null ?? []; // => []
undefined ?? []; // => []