zod-from-json-schema

A library that creates Zod types from JSON Schema at runtime. This is in contrast to json-schema-to-zod, which generates JavaScript source code.

Installation

npm install zod-from-json-schema

Usage

This package supports both ESM and CommonJS formats.

ESM (ES Modules)

import { convertJsonSchemaToZod } from 'zod-from-json-schema';

// Define a JSON Schema
const jsonSchema = {
  $schema: "http://json-schema.org/draft-07/schema#",
  type: "object",
  properties: {
    name: { type: "string", minLength: 2, maxLength: 50 },
    age: { type: "integer", minimum: 0, maximum: 120 },
    email: { type: "string", pattern: "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$" },
    tags: {
      type: "array",
      items: { type: "string" },
      uniqueItems: true,
      minItems: 1
    }
  },
  required: ["name", "email"],
  additionalProperties: false
};

// Convert JSON Schema to Zod schema
const zodSchema = convertJsonSchemaToZod(jsonSchema);

// Use the Zod schema to validate data
try {
  const validData = zodSchema.parse({
    name: "John Doe",
    email: "john@example.com",
    age: 30,
    tags: ["user", "premium"]
  });
  console.log("Valid data:", validData);
} catch (error) {
  console.error("Validation error:", error);
}

CommonJS

const { convertJsonSchemaToZod } = require('zod-from-json-schema');

// Define a JSON Schema
const jsonSchema = {
  $schema: "http://json-schema.org/draft-07/schema#",
  type: "object",
  properties: {
    name: { type: "string", minLength: 2, maxLength: 50 },
    age: { type: "integer", minimum: 0, maximum: 120 }
  },
  required: ["name"],
  additionalProperties: false
};

// Convert JSON Schema to Zod schema
const zodSchema = convertJsonSchemaToZod(jsonSchema);

// Use the Zod schema to validate data
try {
  const validData = zodSchema.parse({
    name: "John Doe",
    age: 30
  });
  console.log("Valid data:", validData);
} catch (error) {
  console.error("Validation error:", error);
}

API Reference

`convertJsonSchemaToZod(schema)`

Converts a JSON Schema object to a complete Zod schema.

Parameters:
- schema (Object): A JSON Schema object
Returns:
- A Zod schema that validates according to the JSON Schema

`jsonSchemaObjectToZodRawShape(schema)`

Extracts the object properties from a JSON Schema object into a Zod raw shape. This is useful when you want to combine the properties with other Zod object configurations.

Parameters:
- schema (Object): A JSON Schema object that should have a properties field
Returns:
- A ZodRawShape object that can be used with z.object()

Example:

import { jsonSchemaObjectToZodRawShape } from 'zod-from-json-schema';
import { z } from 'zod';

const jsonSchema = {
  properties: {
    name: { type: "string" },
    age: { type: "integer" }
  },
  required: ["name"]
};

// Get just the property definitions
const rawShape = jsonSchemaObjectToZodRawShape(jsonSchema);

// Add custom handling
const customSchema = z.object({
  ...rawShape,
  // Add additional fields not in the JSON Schema
  createdAt: z.date().default(() => new Date())
}).refine(data => data.age > 18, {
  message: "Age must be over 18 to continue"
});

Supported JSON Schema Features

This library supports the following JSON Schema features:

Basic Types

string
number
integer
boolean
null
object (with properties and required fields)
array

String Validations

minLength
maxLength
pattern (regular expressions)

Number Validations

minimum
maximum
exclusiveMinimum
exclusiveMaximum
multipleOf

Array Validations

minItems
maxItems
uniqueItems

Object Validations

required (required properties)
additionalProperties (controls passthrough behavior)

Schema Composition

const (literal values)
enum (enumerated values)
anyOf (union)
allOf (intersection)
oneOf (union)

Additional

description (carried over to Zod schemas)

License

MIT