json-schema-to-zod

Json-Schema-to-Zod

Looking for the exact opposite? Check out zod-to-json-schema

Summary

A runtime package and CLI tool to convert JSON schema (draft 4+) objects or files into Zod schemas in the form of JavaScript code.

Before v2 it used prettier for formatting and json-refs to resolve schemas. To replicate the previous behaviour, please use their respective CLI tools.

Since v2 the CLI supports piped JSON.

Usage

Online

Just paste your JSON schemas here!

CLI

Simplest example

npm i -g json-schema-to-zod

json-schema-to-zod -i mySchema.json -o mySchema.ts

Example with $refs resolved and output formatted

npm i -g json-schema-to-zod json-refs prettier

json-refs resolve mySchema.json | json-schema-to-zod | prettier --parser typescript > mySchema.ts

Options

Flag	Shorthand	Function
--input	-i	JSON or a source file path (required if no data is piped)
--output	-t	Target file name
--name	-n	The name of the schema in the output
--depth	-d	Maximum depth of recursion in schema before falling back to z.any(). Defaults to 0. `
--module	-m	Force module syntax ("esm" or "cjs")

Programmatic

jsonSchemaToZod will output the full module code, including a Zod import. If you only need the Zod schema itself, try one of the parsers directly. If you need to deref your JSON schema, try using json-refs resolve function before passing in the schema.

import { jsonSchemaToZod, parseSchema } from "json-schema-to-zod";

const myObject = {
  type: "object",
  properties: {
    hello: {
      type: "string",
    },
  },
} as const;

const module = jsonSchemaToZod(myObject);

const schema = parseSchema(myObject);

module

import { z } from "zod";

export default z.object({ hello: z.string().optional() });

schema

z.object({ hello: z.string().optional() });

Overriding a parser

You can pass a ParserOverride to the overrideParser option, which is a function that receives the current schema node and the reference object, and should return a string when it wants to replace a default output. If the default output should be used for the node, just return nothing.

Use at Runtime

The output of this package is not meant to be used at runtime. JSON Schema and Zod does not overlap 100% and the scope of the parsers are purposefully limited in order to help the author avoid a permanent state of chaotic insanity. As this may cause some details of the original schema to be lost in translation, it is instead recommended to use tools such as (Ajv)[https://ajv.js.org/] to validate your runtime values directly against the original JSON Schema.

That said, it's possible in most cases to use eval. Here's an example that you shouldn't use:

const zodSchema = eval(jsonSchemaToZod({ type: "string" }, { module: "cjs" }));

zodSchema.safeParse("Please just use Ajv instead");