Add EmptyArray and IsEmptyArray types#1355
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sindresorhus
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Feb 9, 2026
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| // IsEmptyArray — Edge cases | ||
| expectType<IsEmptyArray<any>>(false); | ||
| expectType<IsEmptyArray<never>>(false); |
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Some more tests:
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| expectType<IsEmptyArray<never>>(false); | |
| expectType<IsEmptyArray<never>>(false); | |
| // IsEmptyArray — Union behavior | |
| expectType<IsEmptyArray<[] | [1]>>({} as boolean); | |
| expectType<IsEmptyArray<readonly [] | readonly [1]>>({} as boolean); | |
| // IsEmptyArray — More non-empty/array boundaries | |
| expectType<IsEmptyArray<[never]>>(false); | |
| expectType<IsEmptyArray<unknown[]>>(false); | |
| expectType<IsEmptyArray<any[]>>(false); |
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Maybe also:
// @ts-expect-error
emptyArray.length = 1;
sindresorhus
reviewed
Feb 9, 2026
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| @category Array | ||
| */ | ||
| export type EmptyArray = never[]; |
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Why not
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| export type EmptyArray = never[]; | |
| export type EmptyArray = []; |
?
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All addressed — simplified to [], added union/boundary tests, and the length immutability test.
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Closes #929
Adds
EmptyArray(never[]) for representing a strictly empty array, analogous toEmptyObject. Also addsIsEmptyArray<T>as a type guard.IsEmptyArrayhandles:[],never[],readonly [],readonly never[]→truestring[],any,never→falseThis picks up where #931 left off, with the readonly array tests that were requested in review.