Variable isErr`Const`

isErr: <R extends UnknownResult>(result: R) => result is NarrowToErr<R>

Type guard for the error variant.

Type Declaration

- <R extends UnknownResult>(result: R): result is NarrowToErr<R>
- Type Parameters
  - R extends UnknownResult
  Parameters
  - result: R
  Returns result is NarrowToErr<R>

Example

const operation = Result.ok(3);

const failure = Result.err('error');

if (Result.isOk(operation)) {
  const value: number = operation.value;

  assert.isTrue(value === 3);
}

assert.isTrue(Result.isErr(failure));