Extracting values

Leave Result safely with match or a fallback, and understand when unwrap throws.

Prefer match at handling boundaries

const response = result.match({
  ok: (value) => Response.json(value, { status: 200 }),
  err: (error) => toErrorResponse(error),
});

Both branches are visible and the output type is unified.

Provide a fallback with unwrapOr

const port = parsePort(input).unwrapOr(3000);
// number

The fallback may have a different type, so the result is the union of the success and fallback types.

Static forms:

Result.unwrapOr(result, defaultValue);
Result.unwrapOr(defaultValue)(result);

Assert success with unwrap

const value = result.unwrap();
const value = result.unwrap("Configuration must be valid at startup");

On Err, unwrap throws Panic; the error value is preserved as its cause. Use this only where an Err proves an invariant is broken or where an outer defect boundary intentionally terminates the operation.

Do not unwrap routine failures

Avoid:

const user = findUser(id).unwrap(); // missing user is expected

Handle or propagate instead:

const greeting = findUser(id).map((user) => `Hello, ${user.name}`);