type MapKey<BaseType> = BaseType extends Map<infer KeyType, unknown> ? KeyType : never;
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type MapValue<BaseType> = BaseType extends Map<unknown, infer ValueType> ? ValueType : never;
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export type ArrayEntry<BaseType extends readonly unknown[]> = [number, BaseType[number]];
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export type MapEntry<BaseType> = [MapKey<BaseType>, MapValue<BaseType>];
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export type ObjectEntry<BaseType> = [keyof BaseType, BaseType[keyof BaseType]];
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export type SetEntry<BaseType> = BaseType extends Set<infer ItemType> ? [ItemType, ItemType] : never;
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/**
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Many collections have an `entries` method which returns an array of a given object's own enumerable string-keyed property [key, value] pairs. The `Entry` type will return the type of that collection's entry.
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|
For example the {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries|`Object`}, {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/entries|`Map`}, {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/entries|`Array`}, and {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/entries|`Set`} collections all have this method. Note that `WeakMap` and `WeakSet` do not have this method since their entries are not enumerable.
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|
@see `Entries` if you want to just access the type of the array of entries (which is the return of the `.entries()` method).
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|
@example
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```
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import {Entry} from 'type-fest';
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|
interface Example {
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someKey: number;
|
}
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const manipulatesEntry = (example: Entry<Example>) => [
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// Does some arbitrary processing on the key (with type information available)
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example[0].toUpperCase(),
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|
// Does some arbitrary processing on the value (with type information available)
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example[1].toFixed(),
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];
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const example: Example = {someKey: 1};
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const entry = Object.entries(example)[0] as Entry<Example>;
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const output = manipulatesEntry(entry);
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|
// Objects
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const objectExample = {a: 1};
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const objectEntry: Entry<typeof objectExample> = ['a', 1];
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// Arrays
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const arrayExample = ['a', 1];
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const arrayEntryString: Entry<typeof arrayExample> = [0, 'a'];
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const arrayEntryNumber: Entry<typeof arrayExample> = [1, 1];
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|
// Maps
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const mapExample = new Map([['a', 1]]);
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const mapEntry: Entry<typeof mapExample> = ['a', 1];
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|
// Sets
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const setExample = new Set(['a', 1]);
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const setEntryString: Entry<typeof setExample> = ['a', 'a'];
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const setEntryNumber: Entry<typeof setExample> = [1, 1];
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```
|
*/
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export type Entry<BaseType> =
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BaseType extends Map<unknown, unknown> ? MapEntry<BaseType>
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: BaseType extends Set<unknown> ? SetEntry<BaseType>
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: BaseType extends unknown[] ? ArrayEntry<BaseType>
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: BaseType extends object ? ObjectEntry<BaseType>
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: never;
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