How the JSON to TypeScript Converter Works

TypeScript's power comes from its type system. But manually writing interfaces for API responses or complex data structures is tedious. This converter does it instantly.

Type Inference

The converter maps JSON types to TypeScript types automatically. It examines values to determine the most appropriate type.

Nested Interface Generation

Nested objects become separate interfaces with PascalCase names derived from the property key. This keeps interfaces clean and reusable.

{
  "user": {
    "name": "John",
    "settings": {
      "theme": "dark"
    }
  }
}

export interface Root {
  user: User;
}

export interface User {
  name: string;
  settings: Settings;
}

export interface Settings {
  theme: string;
}

Array Type Inference

The converter examines the first element of arrays to determine the array item type. Empty arrays become unknown[] since there's no data to infer from.

export interface Root {
  tags: string[];        // ["a", "b"] → string[]
  users: UserItem[];     // [{...}] → generates UserItem interface
  empty: unknown[];      // [] → unknown[]
}

Optional Properties

Properties with null or undefined values are marked as optional using the ? modifier. This correctly represents nullable fields in your type definitions.

export interface User {
  name: string;
  nickname?: null;  // Optional because value is null
}

Property Name Handling

Property names that aren't valid JavaScript identifiers (containing spaces, starting with numbers, etc.) are automatically quoted.

export interface Root {
  validName: string;
  "invalid-name": string;
  "123numeric": number;
}

Deduplication

The converter tracks generated interface names to avoid duplicates. If the same structure appears multiple times, it reuses the existing interface name.