When To Use the ?? And || In JavaScript — The ?? (nullish coalescing) and || (logical OR) operators in JavaScript provide default values when the left-hand side expression is not provided. The ?? operator only checks for null and undefined, allowing other falsy values like 0, false, or an empty string to remain. The || operator checks for all falsy values. The ?? operator is particularly useful for APIs, optional parameters, or dynamic data that may not always be defined.