valueOrDefault

ValueOrDefault is a programming pattern and, in some languages, a utility that returns a given value if it is not null or undefined; otherwise, it returns a specified default value. It is commonly used to simplify handling optional data and to prevent null reference errors.

In practice, valueOrDefault can be implemented as a small helper or realized through language features. Different languages offer analogous constructs: JavaScript and TypeScript provide the nullish coalescing operator a ?? b, which yields a when a is not null or undefined, else b; for example, userName ?? 'Guest'. Python uses a conditional expression like value if value is not None else default. Kotlin uses the Elvis operator value ?: default. C# also offers a null-coalescing operator, enabling expressions that return the left value when present or a default on null. Other languages provide similar concepts via Optional types and methods such as orElse, unwrapOr, or defaultValue.

Common use cases include supplying defaults for configuration values, function parameters, and UI labels when input data may be missing. They are also used to create robust data pipelines where missing fields should not derail processing.

Caveats include distinguishing between null/undefined and other falsey values. A value of 0, an empty string, or false may be meaningful and should not be replaced unless that behavior is intended. When a default should apply for any falsy value, a broader check or explicit handling is required.

See also: null-coalescing operator, Elvis operator, Optional type.