--- title: Please avoid repeating type guard. | daily.dev description: is-kit is a JavaScript/TypeScript library that lets developers compose reusable type guards using combinators like `or()`. Instead of repeatedly writing inline... canonical: https://daily.dev/posts/please-avoid-repeating-type-guard--4hmo2nr6d twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Please avoid repeating type guard. | daily.dev og:description: is-kit is a JavaScript/TypeScript library that lets developers compose reusable type guards using combinators like `or()`. Instead of repeatedly writing inline... og:url: https://daily.dev/posts/please-avoid-repeating-type-guard--4hmo2nr6d og:image: https://api.daily.dev/og/posts/4HMo2nr6D.png og:image:alt: Please avoid repeating type guard. 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. # Please avoid repeating type guard. **[nyaomaru](https://daily.dev/sources/graxwfjk0eop4zs3tdzdr)** · [@nyaomaru](https://daily.dev/nyaomaru) · 1 min read · 0 upvotes · 0 comments ## Summary is-kit is a JavaScript/TypeScript library that lets developers compose reusable type guards using combinators like `or()`. Instead of repeatedly writing inline checks such as `isString(value) || isNumber(value)`, you can create a named, composable guard like `const isTextOrNumber = or(isString, isNumber)` that can be reused, passed to `filter`, and composed further. ## Content Instead of repeatedly writing 👇 isString(value) || isNumber(value) is-kit lets you create a reusable guard 👇 const isTextOrNumber = or(isString, isNumber) Small difference, but now the guard can be named, reused, passed to filter, and composed again. 🧩 [https://github.com/nyaomaru/is-kit](https://github.com/nyaomaru/is-kit) ## Similar posts on daily.dev - [How to Defend Your JavaScript App Against Unsafe Data with TypeScript Guard Utilities](https://daily.dev/posts/how-to-defend-your-javascript-app-against-unsafe-data-with-typescript-guard-utilities-cuooqjnij) · freeCodeCamp · 5 upvotes · 1 comments --- Tags: [#typescript](https://daily.dev/tags/typescript), [#functional-programming](https://daily.dev/tags/functional-programming) [View this post on daily.dev](https://daily.dev/posts/please-avoid-repeating-type-guard--4hmo2nr6d) ```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":"DiscussionForumPosting","mainEntityOfPage":"https://daily.dev/posts/please-avoid-repeating-type-guard--4hmo2nr6d","headline":"Please avoid repeating type guard.","text":"is-kit is a JavaScript/TypeScript library that lets developers compose reusable type guards using combinators like `or()`. Instead of repeatedly writing inline checks such as `isString(value) || isNumber(value)`, you can create a named, composable guard like `const isTextOrNumber = or(isString, isNumber)` that can be reused, passed to `filter`, and composed further.","url":"https://daily.dev/posts/please-avoid-repeating-type-guard--4hmo2nr6d","datePublished":"2026-08-09T15:10:26.490Z","dateModified":"2026-08-09T15:10:44.113Z","author":{"@type":"Person","name":"nyaomaru","url":"https://daily.dev/nyaomaru","image":"https://avatars.githubusercontent.com/u/90489696?v=4","interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"EndorseAction"},"userInteractionCount":280}},"interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"isPartOf":{"@type":"WebPage","url":"https://daily.dev/sources/graxwfjk0eop4zs3tdzdr","name":"nyaomaru"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"nyaomaru","item":"https://daily.dev/sources/graxwfjk0eop4zs3tdzdr"},{"@type":"ListItem","position":3,"name":"Please avoid repeating type guard."}]} ```