Paseri

A TypeScript parsing and validation library for structured data. Ensure that untrusted input from users or external APIs conforms to the expected format.

Why the name? It’s the Japanese name for parsley (パセリ), and also a play on words on parse/parsing, which is the goal of this library.

Acknowledgements

Zod

Paseri is heavily inspired by Zod 🔗’s expressive API. While Zod is the industry standard for general-purpose validation, Paseri was built to bring that same developer experience to performance-critical applications and environments where Zod’s architecture may be a bottleneck — all while maintaining a zero-compromise approach to security.

Valita

Valita 🔗 sets the high water-mark for performance in the TypeScript ecosystem¹. Paseri matches or exceeds this raw efficiency while offering a more expansive, Zod-like feature set, and a focus on schema immutability.

Goals

The list may be expanded in time, but for now the objectives are the following:

• Parsing and validation of untrusted input to ensure it conforms to the expected format. A successful result will be typed with the narrowest possible definition to obviate the need to do additional validation at the point of usage².
• High performance¹ and usability in a strict Content Security Policy (CSP) 🔗 environment.
• An API that is reasonably close to that of Zod. One-to-one compatibility is not the intention.
• Immutability of schemas. This avoids a lot of bugs caused by mutating references to non-primitive types.

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Footnotes

1. While higher performance is possible using dynamic code execution (JIT) or ahead-of-time (AOT) compilation, these approaches introduce security risks 🔗 or added build complexity. ↩ ↩²

2. An excellent article 🔗 on the concept of type-driven design. ↩