json-schema-specificity

A JavaScript library for comparing JSON Schema specificity and extending schemas. This library helps determine if one JSON schema is more specific than another, meaning that any JSON document that would be validated by the extension schema would also be validated by the original schema. It also provides functionality to extend schemas by merging them.

Live Demo

Try out the library with our interactive demo. The demo allows you to input two JSON schemas and instantly see if one is more specific than the other.

Installation

npm install json-schema-specificity

Usage

import { isMoreSpecific, extendSchema } from 'json-schema-specificity';

// Check if one schema is more specific than another
const original = {
  type: 'object',
  properties: {
    name: { type: 'string' }
  }
};

const extension = {
  type: 'object',
  properties: {
    name: { type: 'string', minLength: 1 }
  }
};

const isMoreSpecificResult = isMoreSpecific(original, extension);
// result: true (because extension is more specific than original)

// Extend a schema with another
const base = {
  type: 'object',
  properties: {
    user: {
      type: 'object',
      properties: {
        name: { type: 'string' }
      }
    }
  }
};

const delta = {
  properties: {
    user: {
      properties: {
        age: { type: 'number' }
      }
    }
  }
};

const extended = extendSchema(base, delta);
// result: {
//   type: 'object',
//   properties: {
//     user: {
//       type: 'object',
//       properties: {
//         name: { type: 'string' },
//         age: { type: 'number' }
//       }
//     }
//   }
// }

API

isMoreSpecific(original, extension)

Determines if the extension schema is more specific than the original schema.

Parameters

• original (Object): The original JSON schema
• extension (Object): The extension JSON schema to compare

Returns

• boolean: Returns true if the extension schema is more specific than the original schema, false otherwise.

extendSchema(base, extension)

Recursively merges two JSON schemas, with the extension schema overriding or extending the base schema.

Parameters

• base (Object): The base JSON schema
• extension (Object): The extension JSON schema to merge with the base

Returns

• Object: A new object representing the merged schema

Features

• Supports JSON Schema Draft-07
• Handles various schema keywords:
  • Type compatibility (including number/integer relationships)
  • Required properties
  • Property constraints
  • Numeric constraints (minimum, maximum, multipleOf)
  • String constraints (minLength, maxLength, pattern)
  • Array constraints (minItems, maxItems, uniqueItems)
  • Enum values
  • Const values
  • Additional properties
• Schema extension capabilities:
  • Deep merging of nested objects
  • Array handling
  • Primitive value overrides
  • Null/undefined handling

Examples

Type Compatibility

isMoreSpecific(
  { type: 'number' },
  { type: 'integer' }
); // true

Numeric Constraints

isMoreSpecific(
  { type: 'number', minimum: 0, maximum: 100 },
  { type: 'number', minimum: 10, maximum: 50 }
); // true

Array Constraints

isMoreSpecific(
  { type: 'array', items: { type: 'string' }, maxItems: 5 },
  { type: 'array', items: { type: 'string' }, minItems: 1, maxItems: 3 }
); // true

Schema Extension

extendSchema(
  { type: 'object', required: ['name'] },
  { additionalProperties: false }
); // { type: 'object', required: ['name'], additionalProperties: false }

License

ISC

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.