Usage

isSet(new Set([1, 2, 3])); // => true
isSet(new Map([1, 2, 3])); // => false

Installation

CLI

npx atmx add helper is-set

Manually

Copy and paste the following method into @/utils/helpers/isSet.ts:

import { isTagged } from "@/helpers/is-tagged.ts";

import type { StrictExtract } from "@/types/strict-extract.ts";

/**
* Checks if the given value is a Set.
*
* Instances from [other realms][1] are also supported.
*
* [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/instanceof#instanceof_and_multiple_realms
*
* @example
* isSet(new Set([1, 2, 3])) // => true
* isSet(new Map([1, 2, 3])) // => false
*/
export function isSet<Input>(value: Input): value is ExtractSet<Input> {
return isTagged(value, "[object Set]");
}

/**
* An absurdly complicated but accurate type for extracting Set types.
*
* It's like `Extract<T, Set<any>>` but better with edge cases.
*/
export type ExtractSet<T> = T extends any
? [StrictExtract<T, ReadonlySet<unknown>>] extends [ReadonlySet<unknown>]
? Extract<T, ReadonlySet<unknown>>
: [StrictExtract<T, Set<unknown>>] extends [Set<unknown>]
  ? Extract<T, Set<unknown>>
  : Set<unknown> extends T
    ? Set<unknown>
    : never
: never;