39 lines
1.4 KiB
TypeScript
Executable file
39 lines
1.4 KiB
TypeScript
Executable file
/**
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Methods to exclude.
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*/
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type ArrayLengthMutationKeys = 'splice' | 'push' | 'pop' | 'shift' | 'unshift';
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/**
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Create a type that represents an array of the given type and length. The array's length and the `Array` prototype methods that manipulate its length are excluded in the resulting type.
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Please participate in [this issue](https://github.com/microsoft/TypeScript/issues/26223) if you want to have a similiar type built into TypeScript.
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Use-cases:
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- Declaring fixed-length tuples or arrays with a large number of items.
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- Creating a range union (for example, `0 | 1 | 2 | 3 | 4` from the keys of such a type) without having to resort to recursive types.
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- Creating an array of coordinates with a static length, for example, length of 3 for a 3D vector.
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@example
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```
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import {FixedLengthArray} from 'type-fest';
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type FencingTeam = FixedLengthArray<string, 3>;
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const guestFencingTeam: FencingTeam = ['Josh', 'Michael', 'Robert'];
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const homeFencingTeam: FencingTeam = ['George', 'John'];
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//=> error TS2322: Type string[] is not assignable to type 'FencingTeam'
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guestFencingTeam.push('Sam');
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//=> error TS2339: Property 'push' does not exist on type 'FencingTeam'
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```
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*/
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export type FixedLengthArray<Element, Length extends number, ArrayPrototype = [Element, ...Element[]]> = Pick<
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ArrayPrototype,
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Exclude<keyof ArrayPrototype, ArrayLengthMutationKeys>
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> & {
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[index: number]: Element;
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[Symbol.iterator]: () => IterableIterator<Element>;
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readonly length: Length;
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};
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