type-plus
Version:
Provides additional types for TypeScript.
44 lines • 1.98 kB
TypeScript
import type { IsNever } from '../never/never_type.js';
import type { IsUnion } from '../union/union.js';
import type { MergeOptions } from '../utils/options.js';
/**
* 🦴 *utilities*
* 🔢 *customizable*
*
* Filter the element `T` in an array or tuple to match `Criteria`.
*
* @typeParam Options['widen'] Allow using narrow type to match widen type.
* e.g. `number, 1` -> `1 | undefined`.
* Default to `true`.
*
* @typeParam Options['caseNotMatch'] Return value when `T` does not match `Criteria`.
* Default to `never`.
*
* @typeParam Options['caseWiden'] Return value when `widen` is true.
* Default to `Criteria | undefined`.
*
* @typeParam Options['caseUnionNotMatch'] Return value when a branch of the union `T` does not match `Criteria`.
* Default to `never`.
*
* If you want the type to behave more like JavaScript,
* you can override it to return `undefined`.
*
* Since it is a union, the result will be joined to the matched branch as union.
* e.g. `ElementMatch<1 | 2, 1>` -> `1 | undefined`
*/
export type ElementMatch<T, Criteria, Options extends ElementMatch.Options = ElementMatch.DefaultOptions<Criteria>> = [T] extends [Criteria] ? T : (MergeOptions<Options, ElementMatch.DefaultOptions<Criteria>> extends infer C extends Record<keyof ElementMatch.Options, unknown> ? ((T extends Criteria ? T : (C['widen'] extends true ? (Criteria extends T ? C['caseWiden'] : C['caseNotMatch']) : C['caseNotMatch'])) extends infer R ? IsUnion<T, IsNever<R, R, R | C['caseUnionNotMatch']>, R> : C['caseNotMatch']) : never);
export declare namespace ElementMatch {
interface Options {
widen?: boolean | undefined;
caseNotMatch?: unknown;
caseWiden?: unknown;
caseUnionNotMatch?: unknown;
}
interface DefaultOptions<Criteria> {
widen: true;
caseNotMatch: never;
caseWiden: Criteria | undefined;
caseUnionNotMatch: never;
}
}
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