json-to-schema

json-to-schema is a lightweight and powerful utility that generates JSON Schema from a given JSON object. It automatically detects the structure of the JSON, including nested objects and arrays, and generates a corresponding schema that can be used for validation, documentation, and other purposes.

Features

• Generates JSON Schema from any JSON object.
• Handles nested objects and arrays efficiently.
• Supports primitive types such as string, number, boolean, and more.
• Automatically identifies required fields based on non-null/undefined values.
• Handles edge cases such as Date and RegExp.

❤️ Support My Work!

Maintaining this package requires effort and dedication. If this project helped you, consider buying me a coffee or supporting me via PayPal. Every donation helps keep this project alive!

Installation

You can install json-to-schema via npm:

npm install json-to-schema

Usage

Generate schema Against a JSON

import { generateJsonSchema } from 'json-to-schema';

const jsonObject = {
  name: "John Doe",
  age: 30,
  isEmployed: true,
  address: {
    street: "123 Main St",
    city: "Somewhere",
    zipcode: "12345"
  },
  skills: ["JavaScript", "Node.js"]
};

const schema = generateJsonSchema(jsonObject);
console.log(JSON.stringify(schema, null, 2));

Handling Arrays

If your JSON object contains arrays, json-to-schema will handle them correctly by generating the items key instead of properties and required.

Example:

const jsonArray = [
  { "name": "John Doe", "age": 30 },
  { "name": "Jane Smith", "age": 28 }
];

const schema = generateJsonSchema(jsonArray);
console.log(JSON.stringify(schema, null, 2));

Output Schema Example

For the following input:

const jsonObject = {
  name: "John Doe",
  age: 30,
  isEmployed: true,
  address: {
    street: "123 Main St",
    city: "Somewhere",
    zipcode: "12345"
  },
  skills: ["JavaScript", "Node.js"]
};

The generated schema will look like:

{
  "type": "object",
  "properties": {
    "name": { "type": "string" },
    "age": { "type": "number" },
    "isEmployed": { "type": "boolean" },
    "address": {
      "type": "object",
      "properties": {
        "street": { "type": "string" },
        "city": { "type": "string" },
        "zipcode": { "type": "string" }
      },
      "required": ["street", "city", "zipcode"]
    },
    "skills": {
      "type": "array",
      "items": { "type": "string" }
    }
  },
  "required": ["name", "age", "isEmployed", "address", "skills"]
}

Supported Types

• Primitive Types: string, number, boolean, null, undefined
• Objects: Handles nested objects and creates properties for them.
• Arrays: Handles arrays and defines the items key, inferring the type of elements inside the array.

Validate JSON Against a Schema

This package also supports validating JSON data against a schema using Ajv.

Example:

import { generateJsonSchema, validateJsonWithSchema } from "json-to-schema-generator";

const jsonObject = {
  name: "John Doe",
  age: 30,
  isEmployed: true,
};

const schema = generateJsonSchema(jsonObject);

const validationResult = validateJsonWithSchema(jsonObject, schema);
if (validationResult.isValid) {
  console.log("JSON is valid!");
} else {
  console.error("Validation errors:", validationResult.errors);
}

License

This project is licensed under the MIT License. See the LICENSE file for details.