Checkr

Checkr is a TypeScript-based XML validation library for validating XML documents against XSD schemas. It is designed to be lightweight, extensible, and dependency-free beyond pure TypeScript/JavaScript.

Features

• Pure TypeScript: No native dependencies, works in Node.js and browsers.
• Extensible Architecture: Supports plugin-like extensibility.
• Comprehensive Validation: Handles global elements, complex types, attributes, constraints, and more.
• XSD 1.0 Support: Covers basic to intermediate features like xs:sequence, xs:choice, enumerations, and type restrictions.

Installation

npm install @jacksierkstra/checkr

or

yarn add @jacksierkstra/checkr

Usage

import { Checkr } from "@jacksierkstra/checkr";

const xml = `<root><element>Value</element></root>`;
const xsd = `<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
              <xs:element name="root">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name="element" type="xs:string"/>
                  </xs:sequence>
                </xs:complexType>
              </xs:element>
            </xs:schema>`;

const validator = new Checkr();
const validation = validator.validate(xml, xsd);

validation.then(result => {
    console.log('Valid: ', result.valid);
    console.log('Errors: ', result.errors);
});

Validation Pipeline

The validation process consists of multiple pipeline stages:

1. Parsing: Convert XML and XSD into DOM structures.
2. Global Validation: Check elements against global definitions.
3. Node-Level Validation:
   • Type validation (xs:string, xs:integer, etc.)
   • Attribute validation (required vs optional, fixed values)
   • Occurrence constraints (minOccurs, maxOccurs)
   • Enumerations and pattern constraints
4. Choice Validation: Ensure valid xs:choice constraints.
5. Recursive Validation: Validate nested elements and structure.

Supported XSD Features

• ✅ xs:sequence, xs:choice
• ✅ xs:element, xs:complexType
• ✅ xs:enumeration, xs:pattern
• ✅ xs:minLength, xs:maxLength
• ✅ Attribute validation (xs:attribute)
• 🚧 Planned:
  • xs:all
  • xs:extension and xs:restriction
  • xs:key, xs:unique, xs:keyref
  • Namespaced imports (xs:import, xs:include)

Running Tests

To run the test suite:

yarn test

Contributing

Contributions are welcome! Feel free to open issues and pull requests.

License

This project is licensed under the MIT License.

Maintained by @jacksierkstra