TypeScript to JSON Converter

Generate example JSON objects from TypeScript interfaces and types with AI — free, instant, no login required.

TypeScript to JSON conversion generates realistic example JSON objects from your TypeScript interface definitions — useful for API mocking, test fixtures, Storybook stories, and documentation. JS2TS infers the correct JSON shape and example values from your TypeScript types in seconds.

Paste your code, then click Convert

JSON

How to use this tool?

This AI-powered converter generates example JSON objects from TypeScript interfaces and type definitions. Follow these steps:

Paste your TypeScript interface or type definition into the input box on the left.
Click the "Convert" button. The AI generates a valid JSON example object matching the interface shape.
Copy the JSON output from the right panel for use in API mocking, testing, or documentation.

Example: Simple Function

TypeScript

// TypeScript Interface
interface Product {
  id: number;
  name: string;
  price: number;
  inStock: boolean;
  tags: string[];
  dimensions?: {
    width: number;
    height: number;
  };
}

JSON

{
  "id": 42,
  "name": "Wireless Keyboard",
  "price": 79.99,
  "inStock": true,
  "tags": ["electronics", "keyboard", "wireless"],
  "dimensions": {
    "width": 44,
    "height": 15
  }
}

How to Generate JSON from a TypeScript Interface

When building APIs, writing tests, or creating Storybook stories, you need example JSON that matches your TypeScript interface shape. Writing mock JSON by hand means copying every field name from the interface, choosing realistic values for each type, and handling nested objects and arrays manually — tedious and error-prone.

The TypeScript to JSON converter generates example JSON automatically. Paste any TypeScript interface or type and get a realistic JSON object with proper values for strings, numbers, dates, arrays, and nested types in seconds.

Why Convert TypeScript Interfaces to JSON?

→Generate API mock data and fixtures from TypeScript types without writing by hand
→Create Storybook story props that match your component TypeScript interface exactly
→Generate test fixtures for Jest, Vitest, or Playwright tests from TypeScript types
→Document API responses with realistic JSON examples derived from your TypeScript definitions

What the TypeScript to JSON Converter Handles

Interface to JSON object

Type alias to JSON

string → realistic example strings

number → realistic integers/decimals

boolean → true/false

Date → ISO 8601 strings

Optional fields included

Array fields → 2-3 examples

Nested interface objects

Union types → first variant

Enum → first enum value

Readonly and partial types

Frequently Asked Questions

How do I generate JSON from a TypeScript interface?

Paste your TypeScript interface into the converter and click Convert. The AI generates a valid JSON object with realistic example values for each field type. Copy the JSON for use in tests, API mocks, or documentation.

What is TypeScript to JSON conversion used for?

Common uses: generating API mock responses for frontend development, creating test fixtures for Jest or Vitest, populating Storybook stories with typed props, and generating API documentation examples. It converts your type definitions into concrete JSON examples.

Can I convert a TypeScript type alias to JSON?

Yes. Both interface and type aliases are supported: type User = { id: number; name: string } produces the same JSON output as interface User { id: number; name: string }.

How are optional TypeScript fields handled?

Optional fields (field?: Type) are included in the JSON output with example values. If you need to test the case without optional fields, remove them from the output JSON manually.

How are union types converted to JSON?

Union types (string | number, "admin" | "user") use the first or most common variant. String literal unions use the first value. Primitive unions use the primary type.

What is the difference between TypeScript to JSON and JSON to TypeScript?

TypeScript to JSON generates example data from type definitions — useful for mocking. JSON to TypeScript generates type definitions from example data — useful when you have an API response and need to type it. They are complementary tools.

How do Date fields appear in the JSON output?

TypeScript Date type fields are converted to ISO 8601 date strings in JSON: "2024-01-15T10:30:00.000Z". JSON has no native date type — ISO strings are the standard representation.

Can I use the output for API mocking with MSW or json-server?

Yes. The generated JSON is valid and can be used directly as MSW (Mock Service Worker) response data, json-server fixtures, or any other API mocking tool. The shape matches your TypeScript interface exactly.

Is the TypeScript to JSON converter free?

Yes. Completely free, no account or login required. Unlimited conversions.

How are TypeScript enums converted to JSON?

Enum fields use the first enum value as the JSON example: enum Role { Admin = "admin", User = "user" } produces "admin" in the JSON. Numeric enums produce the first numeric value.