type-flat

TypeScript Type Flattening Tool | Recursively parses complex types and generates nested JSON or type declarations.

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🧩 Introduction

type-flat is a TypeScript type flattening tool that recursively parses complex types, including generics, nested objects, and intersection types, and generates structured nested type definitions. It is suitable for:

• Generating type declaration files
• SDK type interfaces
• Automated documentation
• Build tool type analysis

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🚀 Features

• ✅ Recursively parse types and preserve nested structure
• 🧠 Automatically substitute generic parameters, supporting instances like Response<User>
• ⚙️ Merge properties from extended types (extends)
• 🌐 Support cross-file type references
• 📘 Output as JSON or .d.ts type declarations
• 🪶 Lightweight and dependency-free

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🛠️ Installation

npm install type-flat
# or
pnpm add type-flat

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🧑‍💻 CLI Usage

npx type-flat <file> <typeName>

• <file>: Path to the TypeScript file (.ts or .d.ts)
• <typeName>: Type or interface name to flatten

Example

npx type-flat -f example/types.ts -t ResponseOfUser

Output:

{
  "code": "number",
  "message": "string",
  "data": {
    "id": "number",
    "name": "string",
    "profile": {
      "email": "string",
      "address": {
        "city": "string",
        "zip": "number"
      }
    }
  }
}

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🧑‍💻 Programming Interface

import { flatten } from 'type-flat';
import Content from './types.d.ts'

const result = await flatten(Content, 'ResponseOfUser');
console.log(JSON.stringify(result, null, 2));

Cross-file Generic Example

types.ts:

export interface Address { city: string; zip: number; }
export interface Profile { email: string; address: Address; }
export interface User { id: number; name: string; profile: Profile; }
export interface Response<T> { code: number; message: string; data: T; }
export type ResponseOfUser = Response<User>;

Usage:

import { flatten } from 'type-flat';

const res = await flatten(Content, 'ResponseOfUser');
console.log(res);

Output:

{
  "code": "number",
  "message": "string",
  "data": {
    "id": "number",
    "name": "string",
    "profile": {
      "email": "string",
      "address": {
        "city": "string",
        "zip": "number"
      }
    }
  }
}

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🧱 Use Cases

• Automatically generate type declarations before publishing npm packages
• Generate common type interfaces for SDKs or frontend projects
• Extract nested complex types for documentation or tooling pipelines

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📦 Output Format

• Default JSON (nested objects represent type structure)
• Future support for generating .d.ts files

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🪴 License

Apache-2.0 © 2025 hboot