Introducing: @traversable/zod

This content originally appeared on DEV Community and was authored by andrew jarrett

A few weeks ago I released a TypeScript library called @traversable/zod.

This post covers what the library does, and highlights a few of its unique features.

Note:
Currently @traversable/zod only works with the latest version of Zod (v4).

Cover photo credit:
Jack Noble, Mob Psycho 100 モブサイコ100

What makes @traversable/zod different?

@traversable/zod can be used in 2 ways:

Pick one of over 25 transformers available off-the-shelf
Hand-roll your own custom transformer

Off-the-shelf

ᯓ📦 `zx.check`

Converts a Zod schema into a super-performant type-guard
📖 Performance profile

ᯓ📦 `zx.deepClone`

Converts a Zod schema into a "deep copy" function
📖 How I built JavaScript's fastest deep clone function

ᯓ📦 `zx.deepEqual`

Converts a Zod schema into a "deep equal" function
📖 How I built JavaScript's fastest deep equals function

ᯓ📦 `zx.deepPartial`

Makes all the properties of a Zod schema optional
📖 Zod drops deepPartial in v4

ᯓ📦 `zx.toString`

Converts a Zod schema into a string
Useful for testing, codegen, sanity checking

ᯓ📦 `zx.toType`

Converts a Zod schema into a TypeScript type
Preserves schema metadata as JSDoc annotations

ᯓ📦 `zx.makeLens`

🔍 Focus nested values with lenses (getters/setters)
🌈 Reify control flow with prisms (pattern-matchers)
⛰️ Map over containers with traversals (for-loops)
🧱 Stack them together with function composition

Roll your own

ᯓ📦 `zx.fold`

All the off-the-shelf transformers that @traversable/zod ships are powered by zx.fold.

Under the hood, the library uses an abstraction called recursion schemes that make implementing recursion simple and fun.

To demonstrate, I used it to implement toJsonSchema.

The implementation is so minimal (28 lines!) that I've embedded it here, in its entirety:

Note:

I specifically chose toJsonSchema because multiple libraries already exist that do this, including Zod itself.

The goal is to showcase how you can use zx.fold to build a library of your own.

Closing thoughts

Thanks for reading!

If you have any feedback, feature requests, or questions, feel free to open an issue or start a discussion.

What makes @traversable/zod different?

Off-the-shelf

ᯓ📦 zx.check

ᯓ📦 zx.deepClone

ᯓ📦 zx.deepEqual

ᯓ📦 zx.deepPartial

ᯓ📦 zx.toString

ᯓ📦 zx.toType

ᯓ📦 zx.makeLens