A collection of essential TypeScript utility types that should have been built-in.
Type Fest is a library of essential TypeScript utility types that extend the language's built-in type system. It provides developers with robust, well-tested types for common patterns like deep modifications, conditional logic, string manipulation, and numeric operations, solving the problem of having to reinvent or copy-paste complex type definitions.
TypeScript developers building complex type-safe applications, library authors needing advanced type transformations, and teams wanting to enforce consistent type patterns across their codebase.
Developers choose Type Fest because it offers a curated collection of high-quality, battle-tested utility types that are missing from TypeScript's standard library, saving time and reducing errors compared to rolling their own solutions.
A collection of essential TypeScript types
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Provides deep versions of Readonly, Partial, Required, and others for nested structures, as listed in the README, solving complex object transformations without manual recursion.
Includes types like CamelCase and SnakeCase for converting string literal types between cases, both shallowly and deeply, which TypeScript lacks natively.
Offers boolean types such as IsAny, IsNever, and IsUnion for compile-time type introspection, enhancing type safety and validation in advanced scenarios.
Features types like Jsonify and StructuredCloneable for handling JSON serialization and structured cloning in a type-safe manner, addressing common serialization gaps.
Demands TypeScript >=5.9, ES modules, and strict mode, which can block adoption in projects with older setups or CommonJS dependencies.
With over 100 utility types, the library has a steep learning curve and can be difficult to navigate, especially for developers unfamiliar with advanced type concepts.
Complex type transformations, particularly deep nested ones, may increase TypeScript compilation times in large codebases, impacting developer experience.