JSON Swiss

JSON Swiss

JavaScript Class to JSON Schema Generator

Need JSON to JavaScript?
JSON → JavaScript Objects

JavaScript code Input

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JSON Schema Output

Settings

Select which class should be treated as the root when generating the schema.

Parsing runs entirely in your browser. Your source never leaves the page.

Paste your JavaScript class definitions to produce JSON Schema instantly.

Supports ES6 classes with constructor assignments or class field syntax.

How to convert JavaScript classes to JSON Schema – step-by-step guide

This online JavaScript class to JSON Schema converter helps you generate JSON Schema from real models (DTOs, structs, and classes) so you can validate payloads, share contracts, and generate mock JSON.

  1. Step 1 – Paste your JavaScript source

    • Paste the models you want to document into the left editor.
    • Include referenced types in the same snippet so the schema can generate definitions.
    • Use the Sample button to load an example and see the expected input format.

  2. Step 2 – Select the Root class (if needed)

    • If multiple definitions are detected, choose the root that matches your API payload.
    • The output schema is built around the selected root and may include additional definitions for referenced types.

  3. Step 3 – Review the JSON Schema output

    • Check types, required vs. optional fields, and nested object/array structures.
    • Look for definitions and $ref when your models reference other models.
    • Copy or download the schema for validation, documentation, or schema-first development.

  4. Step 4 – Validate or generate mock JSON

    • Click Generate Mock Data to open the mock generator with your schema preloaded.
    • Validate real payloads against your schema to catch breaking changes early.
    • If you rely on advanced schema composition (for example anyOf/oneOf/allOf), verify the result with a full validator like Ajv.

Schema keyword support note

Generated schemas can include $ref and may be edited to include anyOf, oneOf, or allOf. For complex schemas, use a full JSON Schema validator and dereference before mock generation if needed.

Related JSON Schema & code generation tools

Use these tools to validate schemas, generate mock payloads, format JSON examples, and keep code and contracts in sync.

JSON Schema Mock Data Generator

Generate example JSON from your schema for testing, fixtures, and documentation.

JSON Schema Validator

Validate JSON against common schema keywords and find mismatches quickly.

JSON to JavaScript Objects

Turn JSON payloads into reusable JS objects.

JSON to JSON Schema Generator

Build schema from representative JSON samples to complement model-first schemas.

JSON Schema Library

Explore schema examples and patterns for objects, arrays, enums, and constraints.

JSON Formatter

Clean up JSON examples before validating against schema or sharing docs.

Frequently Asked Questions

What JavaScript code is supported?

Paste ES6 classes that assign fields in the constructor (this.field = value) or use class field syntax (field = value). The parser infers JSON Schema types from literal assignments such as strings, numbers, booleans, arrays, and object literals.

How accurate is the type inference?

Literal values set the schema type (for example, "" => string, 0 => integer, [] => array). Non-literal assignments fall back to string and are marked optional. Arrays become schema arrays with generic elements, and object literals become maps.

Does this work with TypeScript?

If your TypeScript classes include literal default values, the parser works as well, but for type annotations we recommend the TypeScript Class → JSON Schema tool. This JavaScript converter focuses on runtime assignments.

How can I get mock JSON from the schema?

After generating the schema, click "Generate Mock Data" to open the Mock Generator with the schema preloaded. Configure locales, array sizes, and optional fields to create example payloads in seconds.

JavaScript to JSON Schema Converter Online | JSONSwiss