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import type {IsNull} from './is-null';
/**
Returns a boolean for whether the given type is `unknown`.
@link https://github.com/dsherret/conditional-type-checks/pull/16
Useful in type utilities, such as when dealing with unknown data from API calls.
@example
```
import type {IsUnknown} from 'type-fest';
// https://github.com/pajecawav/tiny-global-store/blob/master/src/index.ts
type Action<TState, TPayload = void> =
IsUnknown<TPayload> extends true
? (state: TState) => TState,
: (state: TState, payload: TPayload) => TState;
class Store<TState> {
constructor(private state: TState) {}
execute<TPayload = void>(action: Action<TState, TPayload>, payload?: TPayload): TState {
this.state = action(this.state, payload);
return this.state;
}
// ... other methods
}
const store = new Store({value: 1});
declare const someExternalData: unknown;
store.execute(state => ({value: state.value + 1}));
//=> `TPayload` is `void`
store.execute((state, payload) => ({value: state.value + payload}), 5);
//=> `TPayload` is `5`
store.execute((state, payload) => ({value: state.value + payload}), someExternalData);
//=> Errors: `action` is `(state: TState) => TState`
```
@category Utilities
*/
export type IsUnknown<T> = (
unknown extends T // `T` can be `unknown` or `any`
? IsNull<T> extends false // `any` can be `null`, but `unknown` can't be
? true
: false
: false
);
Version data entries
28 entries across 28 versions & 2 rubygems