--- title: Typescript - (ReadOnly)NotEmptyArray | daily.dev description: TypeScript doesn't have a built-in non-empty array type, but you can define one using a tuple type: `type NotEmptyArray = [T, ...T[]]`. This enforces at... canonical: https://daily.dev/posts/typescript---readonly-notemptyarray-d6v5vysb2 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Typescript - (ReadOnly)NotEmptyArray | daily.dev og:description: TypeScript doesn't have a built-in non-empty array type, but you can define one using a tuple type: `type NotEmptyArray = [T, ...T[]]`. This enforces at... og:url: https://daily.dev/posts/typescript---readonly-notemptyarray-d6v5vysb2 og:image: https://api.daily.dev/og/posts/d6V5Vysb2.png og:image:alt: Typescript - (ReadOnly)NotEmptyArray og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Typescript - (ReadOnly)NotEmptyArray **[Playful Programming](https://daily.dev/sources/playfulprogramming)** · [@puppo](https://daily.dev/puppo) · 2 min read · 0 upvotes · 0 comments ## Summary TypeScript doesn't have a built-in non-empty array type, but you can define one using a tuple type: `type NotEmptyArray = [T, ...T[]]`. This enforces at least one element at compile time. To prevent mutation-related issues (e.g., methods that could empty the array), a `ReadOnlyNotEmptyArray` wraps it with `Readonly<>`. A type guard function `isNotEmptyArray` can narrow a regular array to this type at runtime by checking its length. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Bring Immutability and Context to Arrays](https://daily.dev/posts/bring-immutability-and-context-to-arrays-mipldambi) · TypeScript.TV · 13 upvotes · 0 comments - [Beyond the basics: 21 TypeScript features you might not know about](https://daily.dev/posts/beyond-the-basics-21-typescript-features-you-might-not-know-about-oivxxtrie) · DEV · 27 upvotes · 0 comments - [Experiment: making TypeScript immutable-by-default](https://daily.dev/posts/experiment-making-typescript-immutable-by-default-wsz7yxyng) · Hacker News · 0 upvotes · 0 comments - [Unlock the Power of TypeScript’s infer Keyword](https://daily.dev/posts/unlock-the-power-of-typescript-s-infer-keyword-0vrqqnsgq) · This is Learning · 32 upvotes · 2 comments - [Distributive Conditional Types in TypeScript](https://daily.dev/posts/distributive-conditional-types-in-typescript-6tu0eqy5m) · RUBYLAND · 0 upvotes · 0 comments --- Tags: [#javascript](https://daily.dev/tags/javascript), [#typescript](https://daily.dev/tags/typescript) [View this post on daily.dev](https://daily.dev/posts/typescript---readonly-notemptyarray-d6v5vysb2) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Typescript - (ReadOnly)NotEmptyArray","url":"https://daily.dev/posts/typescript---readonly-notemptyarray-d6v5vysb2","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/typescript---readonly-notemptyarray-d6v5vysb2"},"datePublished":"2026-03-16T21:47:45.545Z","dateModified":"2026-03-17T18:00:46.624Z","description":"TypeScript doesn't have a built-in non-empty array type, but you can define one using a tuple type: `type NotEmptyArray = [T, ...T[]]`. 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