TypeScript type guard library is-kit hits 50 GitHub stars, now used in 100k-user app

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is-kit, an open-source TypeScript type guard library maintained by frontend engineer nyaomaru, has surpassed 50 GitHub stars. The library is now deployed in a production TypeScript application that serves more than 100,000 users. The project addresses a common problem where repeated, structurally similar type guard functions create maintenance overhead in larger codebases. Using composable utilities such as define, equalsKey, and or, developers can replace duplicated inline checks with reusable, consistently shaped predicates. The milestone prompted the maintainer to share how the library is applied in real production code, including patterns for handling HTTP client errors and status-code-specific guards.

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