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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.

Installation

deno add jsr:@vbudovski/paseri

bunx jsr add @vbudovski/paseri

pnpx jsr add @vbudovski/paseri

yarn dlx jsr add @vbudovski/paseri

npx jsr add @vbudovski/paseri

Acknowledgements

Zod

This library wouldn't exist without Zod as a source of inspiration, with its incredibly expressive, and straightforward API. Zod is an excellent, and very mature library, and if the highest possible performance isn't a key requirement, then it is a great choice.

Valita

It sets an incredibly high bar for parsing performance, and is the current benchmark for this implementation. Some of the goals of this library differ from the goals of Valita, but it is nonetheless an excellent project.

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 usage¹.
• High performance², 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.

Documentation

https://paseri.dev

Developer guide

Paseri uses the Deno runtime rather than Node, and requires Deno 2.1.4 or later. Packages are published to the JSR registry only, and publishing is performed automatically by CI.

• paseri-lib contains the sources for the library.
• paseri-docs contains the documentation, built with Astro and Starlight.

Setup

After cloning the repository, be sure you set up the git hooks using the following command:

deno task init

Running tests

deno test

Running benchmarks

deno bench

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Footnotes

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

2. It's certainly possible to create much faster parsers using dynamic code execution or ahead-of-time compilation, but they each have drawbacks in the form of potential security issues or added complexity from requiring a manual compilation step. ↩