conditional-types-over-overloads

To define a TypeScript function return type that depends on the input type, use a conditional type within a single generic signature. This automatically maps each input union member to its corresponding output and avoids maintaining multiple overloads.

You should prefer conditional types over overloads to reduce overload proliferation and maintenance overhead. A single conditional signature handles union input types cleanly, distributes over unions automatically, and improves type accuracy across multiple possible outputs.

The best way to handle TypeScript union inputs returning different outputs is a conditional return type. It automatically distributes over the input union, mapping each member to its specific output without creating multiple function overloads.

To create a TypeScript type utility that distributes over unions, define a generic function with a conditional return type. This ensures the utility resolves the signature correctly by processing each union member individually for accurate type mapping.

The limitations of using TypeScript overloads include proliferation and difficult maintenance when return types hinge on inputs. Overloads struggle to handle union inputs cleanly, whereas a conditional type satisfies a single generic signature and improves type accuracy.