Module @traversable/zod - v0.0.20

ᯓ𝘁𝗿𝗮𝘃𝗲𝗿𝘀𝗮𝗯𝗹𝗲/𝘇𝗼𝗱

@traversable/zod or zx is a schema rewriter for zod.

Requirements

@traversable/zod has a peer dependency on zod (v4).

Getting started

$ pnpm add @traversable/zod zod

Here's an example of importing the library:

import { z } from 'zod'
import { zx } from '@traversable/zod'

// see below for specific examples

Fuzz-tested, production ready

Experimental

zx.makeLens (🔬)

Advanced

Features

`zx.check`

zx.check converts a zod-schema into a super-performant type-guard.

Notes

Better performance than z.parse and z.safeParse
Works in any environment that supports defining functions using the Function constructor, including (as of May 2025) Cloudflare workers 🎉

Performance comparison

Here's a Bolt sandbox if you'd like to run the benchmarks yourself.

z.parse and z.safeParse clone the object they're parsing, and return an array of issues if any are encountered.

Those features are useful in certain contexts.

But in contexts where all you need is to know whether a value is valid or not, it'd be nice to have a faster alternative, that doesn't allocate.

zx.check takes a zod schema, and returns a type guard. It's performance is an order of magnitude faster than z.parse and z.safeParse in almost every case.

                     ┌─────────────────┐
                     │        Average  │
┌────────────────────┼─────────────────┤
│  z.parse (v4)      │  20.41x faster  │
├────────────────────┼─────────────────┤
│  z.safeParse (v4)  │  21.05x faster  │
└────────────────────┴─────────────────┘

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const Address = z.object({
  street1: z.string(),
  street2: z.optional(z.string()),
  city: z.string(),
})

const addressCheck = zx.check(Address)

addressCheck({ street1: '221B Baker St', city: 'London' }) // => true
addressCheck({ street1: '221B Baker St' })                 // => false

`zx.check.writeable`

zx.check converts a zod-schema into a super-performant type-guard.

Compared to zx.check, zx.check.writeable returns the check function in stringified ("writeable") form.

Notes

Useful when you're consuming a set of zod schemas and writing them all to disc
Also useful for testing purposes or for troubleshooting, since it gives you a way to "see" exactly what the check functions check
Since you're presumably writing to disc a build-time, works with Cloudflare workers

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const addressCheck = zx.check.writeable(
  z.object({
    street1: z.string(),
    street2: z.optional(z.string()),
    city: z.string(),
  }),
  { typeName: 'Address' }
)

console.log(addressCheck) 
// =>
// type Address = { street1: string; street2?: string; city: string; }
// function check(value: Address) {
//   return (
//     !!value &&
//     typeof value === "object" &&
//     typeof value.street1 === "string" &&
//     (!Object.hasOwn(value, "street2") || typeof value?.street2 === "string") &&
//     typeof value.city === "string"
//   );
// }

`zx.deepClone`

zx.deepClone lets users derive a specialized "deep copy" function that works with values that have been already validated.

Because the values have already been validated, clone times are significantly faster than alternatives like window.structuredClone and Lodash.cloneDeep.

Performance comparison

Here's a Bolt sandbox if you'd like to run the benchmarks yourself.

                           ┌─────────────────┐
                           │         (avg)   │
┌──────────────────────────┼─────────────────┤
│  Lodash.cloneDeep        │  30.64x faster  │
├──────────────────────────┼─────────────────┤
│  window.structuredClone  │  50.26x faster  │
└──────────────────────────┴─────────────────┘

This article goes into more detail about what makes zx.deepClone so fast.

Example

import { assert } from 'vitest'
import { z } from 'zod'
import { zx } from '@traversable/zod'

const Address = z.object({
  street1: z.string(),
  street2: z.optional(z.string()),
  city: z.string(),
})

const clone = zx.deepClone(Address)

const sherlock = { street1: '221 Baker St', street2: '#B', city: 'London' }
const harry = { street1: '4 Privet Dr', city: 'Little Whinging' }

const sherlockCloned = clone(sherlock)
const harryCloned = clone(harry)

// values are deeply equal:
assert.deepEqual(sherlockCloned, sherlock) // ✅
assert.deepEqual(harryCloned, harry)       // ✅

// values are fresh copies:
assert.notEqual(sherlockCloned, sherlock)  // ✅
assert.notEqual(harryCloned, harry)        // ✅

`zx.deepClone.writeable`

zx.deepClone lets users derive a specialized "deep clone" function that works with values that have been already validated.

Compared to zx.deepClone, zx.deepClone.writeable returns the clone function in stringified ("writeable") form.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const Address = z.object({
  street1: z.string(),
  street2: z.optional(z.string()),
  city: z.string(),
})

const deepClone = zx.deepClone.writeable(
  z.object({
    street1: z.string(),
    street2: z.optional(z.string()),
    city: z.string(),
  }), 
  { typeName: 'Address' }
)

console.log(deepClone) 
// =>
// type Address = { street1: string; street2?: string; city: string; }
// function deepClone(prev: Address) {
//   return {
//     street1: prev.street1,
//     ...prev.street2 !== undefined && { street2: prev.street2 },
//     city: prev.city
//   }
// }

`zx.deepEqual`

zx.deepEqual lets users derive a specialized "deep equal" function that works with values that have been already validated.

Because the values have already been validated, comparison times are significantly faster than alternatives like NodeJS.isDeepStrictEqual and Lodash.isEqual.

Performance comparison

Here's a Bolt sandbox if you'd like to run the benchmarks yourself.

                             ┌────────────────┬────────────────┐
                             │   Array (avg)  │  Object (avg)  │
┌────────────────────────────┼────────────────┼────────────────┤
│  NodeJS.isDeepStrictEqual  │  40.3x faster  │  56.5x faster  │
├────────────────────────────┼────────────────┼────────────────┤
│  Lodash.isEqual            │  53.7x faster  │  60.1x faster  │
└────────────────────────────┴────────────────┴────────────────┘

This article goes into more detail about what makes zx.deepEqual so fast.

Notes

Works in any environment that supports defining functions using the Function constructor, including (as of May 2025) Cloudflare workers 🎉

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const deepEqual = zx.deepEqual(
  z.object({
    street1: z.string(),
    street2: z.optional(z.string()),
    city: z.string(),
  })
)

deepEqual(
  { street1: '221B Baker St', city: 'London' },
  { street1: '221B Baker St', city: 'London' }
) // => true

deepEqual(
  { street1: '221B Baker St', city: 'London' },
  { street1: '4 Privet Dr', city: 'Little Whinging' }
) // => false

`zx.deepEqual.writeable`

Notes

Useful when you're consuming a set of zod schemas and writing them all to disc
Also useful for testing purposes or for troubleshooting, since it gives you a way to "see" exactly what the deep equal functions are doing

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const deepEqual = zx.deepEqual.writeable(
  z.object({
    street1: z.string(),
    street2: z.optional(z.string()),
    city: z.string(),
  }),
  { typeName: 'Address' }
)

console.log(deepEqual)
// =>
// type Address = { street1: string; street2?: string; city: string; }
// function deepEqual(x: Address, y: Address) {
//   if (x === y) return true;
//   if (x.street1 !== y.street1) return false;
//   if (x.street2 !== y.street2) return false;
//   if (x.city !== y.city) return false;
//   return true;
// }

`zx.deepEqual.classic`

Notes

This option is provided as a fallback in case users cannot work with either #1 or #2

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'
import * as vi from 'vitest'

const deepEqual = zx.deepEqual.classic(
  z.object({
    street1: z.string(),
    street2: z.optional(z.string()),
    city: z.string(),
  })
)

deepEqual(
  { street1: '221B Baker St', city: 'London' },
  { street1: '221B Baker St', city: 'London' },
) // => true

deepEqual(
  { street1: '221B Baker St', city: 'London' },
  { street1: '4 Privet Dr', city: 'Little Whinging' },
) // => false

`zx.fromConstant`

Convert a blob of JSON data into a zod schema that represents its least upper bound.

Example

import { zx } from '@traversable/zod'

let example = zx.fromConstant({ abc: 'ABC', def: [1, 2, 3] })
//  ^? let example: z.ZodType<{ abc: 'ABC', def: [1, 2, 3] }>

console.log(zx.toString(example))
// => z.object({ abc: z.literal("ABC"), def: z.tuple([ z.literal(1), z.literal(2), z.literal(3) ]) })

`zx.fromConstant.writeable`

Convert a blob of JSON data into a stringified zod schema that represents its least upper bound.

Example

import { zx } from '@traversable/zod'

let ex_01 = zx.fromConstant.writeable({ abc: 'ABC', def: [1, 2, 3] })

console.log(ex_01)
// => z.object({ abc: z.literal("ABC"), def: z.tuple([ z.literal(1), z.literal(2), z.literal(3) ]) })

`zx.fromJson`

Convert a blob of JSON data into a zod schema that represents its greatest lower bound.

Example

import type { z } from 'zod'
import { zx } from '@traversable/zod'

let ex_01 = zx.fromJson({ abc: 'ABC', def: [] })
//  ^? let ex_01: z.ZodObject<{ abc: z.ZodString, def: z.ZodArray<z.ZodUnknown> }>

console.log(zx.toString(ex_01))
// => z.object({ abc: z.string(), def: z.array(z.unknown()) })

let ex_02 = zx.fromJson({ abc: 'ABC', def: [123] })
//  ^? let ex_01: z.ZodObject<{ abc: z.ZodString, def: z.ZodArray<z.ZodUnknown> }>

console.log(zx.toString(ex_02))
// => z.object({ abc: z.string(), def: z.array(z.number()) })

let ex_03 = zx.fromJson({ abc: 'ABC', def: [123, null]})
//  ^? let ex_01: z.ZodObject<{ abc: z.ZodString, def: z.ZodArray<z.Union<[z.ZodNumber, z.ZodNull]>> }>

console.log(zx.toString(ex_03))
// => z.object({ abc: z.string(), def: z.array(z.union([z.number(), z.null()])) })

`zx.fromJson.writeable`

Convert a blob of JSON data into a stringified zod schema that represents its greatest lower bound.

Example

import type { z } from 'zod'
import { zx } from '@traversable/zod'

let ex_01 = zx.fromJson.writeable({ abc: 'ABC', def: [] })

console.log(ex_01)
// => z.object({ abc: z.string(), def: z.array(z.unknown()) })

let ex_02 = zx.fromJson.writeable({ abc: 'ABC', def: [123] })

console.log(ex_02)
// => z.object({ abc: z.string(), def: z.array(z.number()) })

let ex_03 = zx.fromJson.writeable({ abc: 'ABC', def: [123, null]})

console.log(ex_03)
// => z.object({ abc: z.string(), def: z.array(z.union([z.number(), z.null()])) })

`zx.deepPartial`

Prior art

Credit goes to @jaens for their work to detect circular schemas and prevent stack overflow.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = zx.deepPartial(z.object({ a: z.number(), b: z.object({ c: z.string() }) }))

type MySchema = z.infer<typeof MySchema>
//   ^? type MySchema = { a?: number, b?: { c?: string } }

`zx.deepPartial.writeable`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = z.object({ a: z.number(), b: z.object({ c: z.string() }) })

console.log(zx.deepPartial.writeable(MySchema))
// =>
// z.object({
//   a: z.number().optional(),
//   b: z.object({
//     c: z.string().optional(),
//     d: z.array(z.boolean()).optional()
//   }).optional()
// }).optional()

`zx.deepRequired`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = zx.deepRequired(z.object({ a: z.number().optional(), b: z.object({ c: z.string().optional() }) }))

type MySchema = z.infer<typeof MySchema>
//   ^? type MySchema = { a: number, b: { c: string } }

`zx.deepRequired.writeable`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = z.object({
  a: z.number().optional(),
  b: z.optional(
    z.object({
      c: z.string(),
      d: z.array(z.boolean()).optional()
    })
  )
})

console.log(zx.deepRequired.writeable(MySchema))
// =>
// z.object({
//   a: z.number(),
//   b: z.object({
//     c: z.string(),
//     d: z.array(z.boolean())
//   })
// })

`zx.deepNullable`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = zx.deepNullable(z.object({ a: z.number(), b: z.object({ c: z.string() }) }))

type MySchema = z.infer<typeof MySchema>
//   ^? type MySchema = { a: number | null, b: { c: string | null } | null }

`zx.deepNullable.writeable`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = z.object({
  a: z.number().optional(),
  b: z.object({
    c: z.string(),
    d: z.array(z.boolean()).optional()
  })
})

console.log(zx.deepNullable.writeable(MySchema))
// =>
// z.object({
//   a: z.number().nullable(),
//   b: z.object({
//     c: z.string().nullable(),
//     d: z.array(z.boolean().nullable()).nullable()
//   }).nullable()
// }).nullable()

`zx.deepNonNullable`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = zx.deepNonNullable(
  z.object({
    a: z.number().nullable(),
    b: z.object({
      c: z.string().nullable(),
    }),
  })
)

type MySchema = z.infer<typeof MySchema>
//   ^? type MySchema = { a: number, b: { c: string } }

`zx.deepNonNullable.writeable`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = z.object({
  a: z.number().nullable(),
  b: z.object({
    c: z.string().nullable(),
  })
})

console.log(zx.deepNonNullable.writeable(MySchema))
// =>
// z.object({
//   a: z.number(),
//   b: z.object({
//     c: z.string(),
//   })
// })

`zx.deepReadonly`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = zx.deepReadonly(z.object({ a: z.number(), b: z.object({ c: z.string() }) }))

type MySchema = z.infer<typeof MySchema>
//   ^? type MySchema = { readonly a: number, readonly b: { readonly c: string } }

`zx.deepReadonly.writeable`

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = z.object({ a: z.number(), b: z.object({ c: z.string() }) })

console.log(zx.deepReadonly.writeable(MySchema))
// =>
// z.object({
//   a: z.number().readonly(),
//   b: z.object({
//     c: z.string().readonly(),
//   }.readonly())
// }.readonly())

`zx.defaultValue`

zx.defaultValues converts a zod schema into a "default value' that respects the structure of the schema.

A common use case for zx.defaultValue is creating default values for forms.

Note

By default, zx.defaultValue does not make any assumptions about what "default" means for primitive types, which is why it returns undefined when it encounters a leaf value. This behavior is configurable.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

const MySchema = z.object({
  a: z.number(),
  b: z.object({
    c: z.string(),
    d: z.array(z.boolean())
  })
})

// by default, primitives are initialized as `undefined`:
const defaultOne = zx.defaultValue(MySchema)
console.log(defaultOne) // => { a: undefined, b: { c: undefined, d: [] } }

// to configure this behavior, use the `fallbacks` property:
const defaultTwo = zx.defaultValue(MySchema, { fallbacks: { number: 0, string: '' } })
console.log(defaultTwo) // => { a: 0, b: { c: '', d: [] } }

`zx.toPaths`

zx.toPaths converts a zod schema into an array of "paths" that represent the schema.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

console.log(
  zx.toPaths(z.object({ a: z.object({ c: z.string() }), b: z.number() }))
) // => [["a", "c"], ["b"]]

`zx.toString`

Convert a zod schema into a string that constructs the same zod schema.

Useful for writing/debugging tests that involve randomly generated schemas.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

console.log(
  zx.toString(
    z.templateLiteral([1n])
  )
) // => z.templateLiteral([1n])

console.log(
  zx.toString(
    z.map(z.array(z.boolean()), z.set(z.number().optional()))
  )
) // => z.map(z.array(z.boolean()), z.set(z.number().optional()))

console.log(
  zx.toString(
    z.tuple([
      z.number().min(0).lt(2),
      z.number().multipleOf(2).nullable(),
    ])
  )
) // => z.tuple([z.number().min(0).lt(2), z.number().multipleOf(2).nullable()])

`zx.toType`

Convert a zod schema into a string that represents its type.

To preserve JSDoc annotations for object properties, pass preserveJsDocs: true in the options object. If the property's metadata includes an example property, the example will be escaped and included as an @escape tag.

Note

By default, the type will be returned as an "inline" type. To give the type a name, use the typeName option.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

console.log(
  zx.toType(
    z.object({
      a: z.optional(z.literal(1)),
      b: z.literal(2),
      c: z.optional(z.literal(3))
    })
  )
) // => { a?: 1, b: 2, c?: 3 }

console.log(
  zx.toType(
    z.intersection(
      z.object({ a: z.literal(1) }),
      z.object({ b: z.literal(2) })
    )
  )
) // => { a: 1 } & { b: 2 }

console.log(
  zx.toType(
    z.templateLiteral([
      z.literal(['a', 'b']),
      ' ',
      z.literal(['c', 'd']),
      ' ',
      z.literal(['e', 'f'])
    ])
  )
) // => "a c e" | "a c f" | "a d e" | "a d f" | "b c e" | "b c f" | "b d e" | "b d f"

// To give the generated type a name, use the `typeName` option:
console.log(
  zx.toType(
    z.object({ a: z.optional(z.number()) }),
    { typeName: 'MyType' }
  )
) // => type MyType = { a?: number }

// To preserve JSDoc annotations, use the `preserveJsDocs` option:
console.log(
  zx.toType(
    z.object({
      street1: z.string().meta({ describe: 'Street 1 name' }),
      street2: z.string().optional().meta({ describe: 'Street 2 name', example: 'Unit B' }),
      city: z.string(),
    }),
    { typeName: 'Address', preserveJsDocs: true }
  )
) 
// => 
// type Address = {
//   /**
//    * Street 1 name
//    */
//   street1: string 
//   /**
//    * Street 2 name
//    * @example "Unit B"
//    */
//   street2?: string
//   city: string
// }

`zx.typeof`

zx.typeof returns the "type" (or tag) of a zod schema.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

console.log(zx.typeof(z.string())) // => "string"

`zx.tagged`

zx.tagged lets you construct a type-guard that identifies the type of zod schema you have.

Example

import { z } from 'zod'
import { zx } from '@traversable/zod'

zx.tagged('object', z.object({})) // true
zx.tagged('array', z.string())    // false

`zx.makeLens`

Note

zx.makeLens still experimental (🔬). Use in production with care.

zx.makeLens accepts a zod schema (classic, v4) as its first argument, and a "selector function" as its second argument.

An optic is a generalization of a lens, but since most people use "lens" to refer to optics generally, they are sometimes used interchangeably in this document.

With zx.makeLens, you use a selector function to build up an optic via a series of property accesses.

Let's look at a few examples to make things more concrete.

Example #1: Lens

For our first example, let's create a lens that focuses on a structure's "a[0]" path:

import { z } from 'zod'
import { zx } from '@traversable/zod'

//////////////////////////
///  example #1: Lens  ///
//////////////////////////

const Schema = z.object({ a: z.tuple([z.string(), z.bigint()]) })

//    Use autocompletion to "select" what you want to focus:
//                                    ↆↆↆↆↆↆ
const Lens = zx.makeLens(Schema, $ => $.a[0])

Lens
// ^? const Lens: zx.Lens<{ a: [string, bigint] }, string>
//                         𐙘___________________𐙘   𐙘____𐙘
//                                     structure         focus

// Lenses have 3 properties:

///////////////
// #1:
// Lens.get -- Given a structure,
//             returns the focus

const ex_01 = Lens.get({ a: ['hi', 0n] })
//                      𐙘_____________𐙘
//                         structure

console.log(ex_01) // => "hi"
//                        𐙘𐙘
//                      focus


///////////////
// #2:
// Lens.set -- Given a new focus and a structure,
//             sets the new focus & returns the structure

const ex_02 = Lens.set(`hey, ho, let's go`, { a: ['', 0n] })
//                      𐙘_______________𐙘    𐙘___________𐙘
//                          new focus          structure

console.log(ex_02) // => { a: ["hey, ho, let's go", 0n] }
//                              𐙘_______________𐙘
//                                  new focus


/////////////////
// #3:
// Lens.modify -- Given a "modify" callback and a structure,
//                applies the callback to the focus & returns the structure

const ex_03 = Lens.modify((str) => str.toUpperCase(), { a: [`hey, ho`, 0n] })
//                         𐙘_______________________𐙘   𐙘__________________𐙘
//                                 callback                 structure

console.log(ex_03) // => { a: ["HEY, HO", 0n] }
//                              𐙘_____𐙘
//                             new focus

// Note that if your callback changes the focus type,
// that will be reflected in the return type as well:

const ex_04 = Lens.modify((str) => str.length > 0, { a: ['', 0n] })
//                         𐙘____________________𐙘   𐙘___________𐙘
//                                callback            structure

console.log(ex_04) // => { a: [false, 0n] }
//           ^? const ex_04: { a: [boolean, bigint] }
//                                 𐙘_____𐙘
//                                new focus

Example #2: Prism

When you use zx.makeLens on a union type, you get back a different kind of lens called a prism.

Let's see how prisms differ from lenses:

import { z } from 'zod'
import { zx } from '@traversable/zod'

///////////////////////////
///  example #2: Prism  ///
///////////////////////////

const Schema = z.union([
  z.object({ tag: z.literal('ONE'), ghi: z.number() }),
  z.object({ tag: z.literal('TWO') })
])

// Let's focus on the first union member's "ghi" property.

// If a discriminant can be inferred, autocompletion allows
// you to select that member by its discriminant,
// prefixed by `ꖛ`:
//
//                                       ↆↆↆↆↆ
const Prism = zx.makeLens(Schema, $ => $.ꖛONE.ghi)

Prism
// ^? Prism: zx.Prism<{ tag: "ONE", ghi: number } | { tag: "TWO" }, number | undefined>
//                     𐙘________________________________________𐙘   𐙘________________𐙘
//                                          structure                          focus

// Prisms have the same 3 properties as lenses,
// but they behave like **pattern matchers**
// instead of _property accessors_

///////////////
// #1:
// Prism.get -- Given a matching structure,
//              returns the focus

const ex_01 = Prism.get({ tag: 'ONE', ghi: 123 })
//                       𐙘____________________𐙘
//                            structure

console.log(ex_01) // => 123
//                       𐙘𐙘𐙘
//                      focus

// Prism.get -- If the match fails,
//              returns undefined

const ex_02 = Prism.get({ tag: 'TWO' })
//                       𐙘___________𐙘
//                         structure

console.log(ex_02) // => undefined
//                          𐙘𐙘𐙘
//                       no match


///////////////
// #2:
// Prism.set -- Given a new focus and a matching structure,
//              sets the new focus & returns the structure

const ex_03 = Prism.set(9_000, { tag: 'ONE', ghi: 123 })
//                      𐙘___𐙘   𐙘____________________𐙘
//                    new focus        structure

console.log(ex_03) // => { tag: 'ONE', ghi: 9000 }
//                                          𐙘__𐙘
//                                        new focus

// Prism.set -- If the match fails,
//              returns the structure unchanged

const ex_04 = Prism.set(9000, { tag: 'TWO' })

console.log(ex_04) // => { tag: 'TWO' }
//                        𐙘__________𐙘
//                          no match


//////////////////
// #3:
// Prism.modify -- Given a "modify" callback and a matching structure,
//                 applies the callback to the focus & returns the structure

// Just like with lenses, if your callback changes the focus type,
// that will be reflected in the return type:

const ex_05 = Prism.modify((n) => [n, n], { tag: 'ONE', ghi: 123 })
//                         𐙘___________𐙘   𐙘____________________𐙘
//                            callback           structure

console.log(ex_05) // => { tag: 'ONE', ghi: [123, 123] }
//           ^? const ex_05: { tag: "ONE", ghi: number[] } | { tag: "TWO" }

// Prism.modify -- If the match fails,
//                 returns the structure unchanged

const ex_06 = Prism.modify((n) => n + 1, { tag: 'TWO' })
//                         𐙘__________𐙘   𐙘___________𐙘
//                           callback       structure

console.log(ex_06) // => { tag: 'TWO' }
//           ^? const ex_06: { tag: "ONE", ghi: number } | { tag: "TWO" }

Example #3: Traversal

When you use zx.makeLens on a collection type (such as z.array or z.record), you get back a different kind of lens called a traversal.

Let's see how traversals differ from lenses and prisms:

import { z } from 'zod'
import { zx } from '@traversable/zod'

///////////////////////////////
///  example #3: Traversal  ///
///////////////////////////////

const Schema = z.object({
  a: z.array(
    z.object({
      b: z.number(),
      c: z.string()
    })
  )
})

// Let's focus on the `"b"` property of each of the elements of the structure's `"a"` property:

// To indicate that you want to traverse the array,
// autocomplete the `ᣔꓸꓸ` field:
//                                                  ↆↆ
const Traversal = zx.makeLens(Schema, $ => $ => $.a.ᣔꓸꓸ.b)


Traversal
// ^? Traversal: zx.Traversal<{ a: { b: number, c: string }[] }, number>
//                             𐙘_____________________________𐙘   𐙘____𐙘
//                                       structure               focus

// Traversals have the same 3 properties as lenses and prisms,
// but they behave like **for-of loops**
// instead of _property accessors_ or _patterns matchers_


///////////////
// #1:
// Traversal.get -- Given a matching structure,
//                  returns all of the focuses

const ex_01 = Traversal.get({ a: [{ b: 0, c: '' }, { b: 1, c: '' }] })
//                           𐙘_____________________________________𐙘
//                                         structure

console.log(ex_01) // => [0, 1]
//                        𐙘__𐙘
//                       focus


///////////////
// #2:
// Traversal.set -- Given a new focus and a matching structure, sets all of the elements
//                  of the collection to the new focus & returns the structure

const ex_02 = Traversal.set(9_000, { a: [{ b: 0, c: '' }, { b: 1, c: '' }] })
//                          𐙘___𐙘   𐙘_____________________________________𐙘
//                        new focus               structure

console.log(ex_02) // => { a: [{ b: 9000, c: '' }, { b: 9000, c: '' }] }
//                                  𐙘__𐙘                𐙘__𐙘
//                                new focus           new focus


//////////////////
// #3:
// Traversal.modify -- Given a "modify" callback and a matching structure,
//                     applies the callback to _each_ focus & returns the structure

// Just like with lenses & prisms, if your callback changes the focus type,
// that will be reflected in the return type:

const ex_03 = Traversal.modify((n) => [n, n + 1], { a: [{ b: 0, c: '' }, { b: 1, c: '' }] })
//                             𐙘______________𐙘    𐙘_____________________________________𐙘
//                                 callback                      structure

console.log(ex_03) // => { a: [{ b: [0, 1], c: '' }, { b: [1, 2], c: '' }] }
//           ^? const ex_03: { a: { b: number[], c: string }[] }
//                                     𐙘______𐙘
//                                    new focus

Advanced Features

`zx.fold`

Note

zx.fold is an advanced API.

Use zx.fold to define a recursive traversal of a zod schema. Useful when building a schema rewriter.

zx.fold is a powertool. Most of @traversable/zod uses zx.fold under the hood.

Compared to the rest of the library, it's fairly "low-level", so unless you're doing something pretty advanced you probably won't need to use it directly.

Example

Let's write a function that takes an arbitrary zod schema as input and stringifies it.

Note

This functionality is already available off-the shelf via zx.toString. We'll be building this example from scratch using zx.fold for illustrative purposes.

import { zx } from '@traversable/zod'

const toString = zx.fold<string>((x) => {
  //                     𐙘____𐙘 this type parameter fills in the "holes" below
  switch (true) {
    case zx.tagged('null')(x): return 'z.null()'
    case zx.tagged('number')(x): return 'z.number()'
    case zx.tagged('string')(x): return 'z.string()'
    case zx.tagged('boolean')(x): return 'z.boolean()'
    case zx.tagged('undefined')(x): return 'z.undefined()'
    case zx.tagged('array')(x): return `${x._zod.def.element}.array()`
    //                                                 ^? method element: string
    case zx.tagged('optional')(x): return `${x._zod.def.innerType}.optional()`
    //                                                     ^? method innerType: string
    case zx.tagged('tuple')(x): return `z.tuple([${x._zod.def.items.join(', ')}])`
    //                                                         ^? method items: string[]
    case zx.tagged('record')(x): return `z.record(${x._zod.def.keyType}, ${x._zod.def.valueType})`
    //                                                            ^? method keyType: string
    case zx.tagged('object')(x): 
      return `z.object({ ${Object.entries(x._zod.def.shape).map(([k, v]) => `${k}: ${v}`).join(', ')} })`
    //                                                ^? method shape: { [x: string]: string }
    default: throw Error(`Unimplemented: ${x._zod.def.type}`)
    //              ^^ there's nothing stopping you from implementing the rest!
  }
})

// Let's test it out:

console.log(
  zx.toString(
    z.object({ A: z.array(z.string()), B: z.optional(z.tuple([z.number(), z.boolean()])) })
  )
)
// => z.object({ A: z.array(z.string()), B: z.optional(z.tuple([z.number(), z.boolean()])) })

Our "naive" implementation is actually more robust than it might seem -- in fact, that's how zx.toString is actually defined.

`zx.Functor`

Note

zx.Functor is an advanced API

zx.Functor is the primary abstraction that powers @traversable/zod.

zx.Functor is a powertool. Most of @traversable/zod uses zx.Functor under the hood.

Compared to the rest of the library, it's fairly "low-level", so unless you're doing something pretty advanced you probably won't need to use it directly.

Namespaces

check
deepClone
deepNonNullable
deepNullable
deepOptional
deepPartial
deepReadonly
deepRequired
toPaths
toString
toType
zx

Type Aliases

deepNonNullable
deepNullable
deepOptional
deepPartial
deepReadonly
deepRequired
defaultValue
fromJson
RAISE_ISSUE_URL
VERSION
ZOD_CHANGELOG

Variables

fold
Functor
isOptional
isOptionalDeep
RAISE_ISSUE_URL
tagged
typeof
VERSION
ZOD_CHANGELOG
ZOD_VERSION

Functions

check
deepClone
deepEqual
deepNonNullable
deepNullable
deepOptional
deepPartial
deepReadonly
deepRequired
defaultValue
fromConstant
fromJson
getFallback
getSubSchema
makeLens
parsePath
toPaths
toString
toType

Module @traversable/zod - v0.0.20

ᯓ𝘁𝗿𝗮𝘃𝗲𝗿𝘀𝗮𝗯𝗹𝗲/𝘇𝗼𝗱

Requirements

Getting started

Table of contents

Fuzz-tested, production ready

Experimental

Advanced

Features

zx.check

Notes

Performance comparison

Example

See also

zx.check.writeable

Notes

Example

See also

zx.deepClone

Performance comparison

Example

See also

zx.deepClone.writeable

Example

See also

zx.deepEqual

Performance comparison

Notes

Example

See also

zx.deepEqual.writeable

Notes

Example

See also

zx.deepEqual.classic

Notes

Example

See also

zx.fromConstant

Example

See also

zx.fromConstant.writeable

Example

See also

zx.fromJson

Example

See also

zx.fromJson.writeable

Example

See also

zx.deepPartial

Prior art

Example

See also

zx.deepPartial.writeable

Example

See also

zx.deepRequired

Example

See also

zx.deepRequired.writeable

Example

See also

zx.deepNullable

Example

See also

zx.deepNullable.writeable

Example

See also

zx.deepNonNullable

Example

See also

zx.deepNonNullable.writeable

Example

See also

zx.deepReadonly

Example

See also

zx.deepReadonly.writeable

Example

`zx.check`

`zx.check.writeable`

`zx.deepClone`

`zx.deepClone.writeable`

`zx.deepEqual`

`zx.deepEqual.writeable`

`zx.deepEqual.classic`

`zx.fromConstant`

`zx.fromConstant.writeable`

`zx.fromJson`

`zx.fromJson.writeable`

`zx.deepPartial`

`zx.deepPartial.writeable`

`zx.deepRequired`

`zx.deepRequired.writeable`

`zx.deepNullable`

`zx.deepNullable.writeable`

`zx.deepNonNullable`

`zx.deepNonNullable.writeable`

`zx.deepReadonly`

`zx.deepReadonly.writeable`

`zx.defaultValue`

`zx.toPaths`

`zx.toString`

`zx.toType`

`zx.typeof`

`zx.tagged`

`zx.makeLens`

`zx.fold`

`zx.Functor`