Function isErr

isErr<T, E = Error>(result: Result<T, E>): result is Err<E>
Type guard to check if a Result is an error.
Type Parameters
- T
  The type of the successful value
- E = Error
  The type of the error
Parameters
- result: Result<T, E>
  The Result to check
Returns result is Err<E>
True if the Result is an error (Err), false otherwise
Example
```
const errorResult = err(new Error("Failed"))
if (isErr(errorResult)) {
  console.error(errorResult.error) // TypeScript knows this is Err
}
```
- Defined in index.ts:134