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1 | /**
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2 | Methods to exclude.
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3 | */
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4 | type ArrayLengthMutationKeys = 'splice' | 'push' | 'pop' | 'shift' | 'unshift';
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5 |
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6 | /**
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7 | 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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8 |
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9 | 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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10 |
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11 | Use-cases:
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12 | - Declaring fixed-length tuples or arrays with a large number of items.
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13 | - 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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14 | - Creating an array of coordinates with a static length, for example, length of 3 for a 3D vector.
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15 |
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16 | @example
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17 | ```
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18 | import {FixedLengthArray} from 'type-fest';
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19 |
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20 | type FencingTeam = FixedLengthArray<string, 3>;
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21 |
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22 | const guestFencingTeam: FencingTeam = ['Josh', 'Michael', 'Robert'];
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23 |
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24 | const homeFencingTeam: FencingTeam = ['George', 'John'];
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25 | //=> error TS2322: Type string[] is not assignable to type 'FencingTeam'
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26 |
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27 | guestFencingTeam.push('Sam');
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28 | //=> error TS2339: Property 'push' does not exist on type 'FencingTeam'
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29 | ```
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30 | */
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31 | export type FixedLengthArray<Element, Length extends number, ArrayPrototype = [Element, ...Element[]]> = Pick<
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32 | ArrayPrototype,
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33 | Exclude<keyof ArrayPrototype, ArrayLengthMutationKeys>
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34 | > & {
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35 | [index: number]: Element;
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36 | [Symbol.iterator]: () => IterableIterator<Element>;
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37 | readonly length: Length;
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38 | };
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