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: "[e-mail]",
    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