TypeScript Callback Transformer

Transform TypeScript declaration files by generating simplified callback parameter overloads.

Overview

This tool automatically processes TypeScript declaration (.d.ts) files to generate additional function or method overloads for callback parameters. It reduces the number of parameters in callback types, making your type definitions more flexible and user-friendly.

For example, if a function in a .d.ts file accepts a callback with multiple parameters, this tool will generate additional overloads where the callback takes fewer parameters (when valid). This is especially useful for libraries that want to provide ergonomic callback signatures for their users.

Features

• Analyzes .d.ts files for functions and methods with callback parameters.
• Generates new overloads with reduced callback parameters, when safe.
• Writes the transformed declarations back to the same file.

Installation

Install globally (optional):

npm install -g typescript-callback-transformer

Or use it directly with npx (no install needed):

npx typescript-callback-transformer <path-to-file.d.ts>

Or, for development (clone and run locally):

git clone https://github.com/topce/typescript-callback-transformer.git
cd typescript-callback-transformer
npm install
npm run dev -- <path-to-file.d.ts>

Example

Suppose you have a declaration file example.d.ts:

declare function foo(cb: (a: number, b: string) => void): void;

After running the transformer:

npm run transform -- example.d.ts

The file will be updated to include additional overloads:

declare function foo(cb: (a: number, b: string) => void): void;
declare function foo(cb: (a: number) => void): void;
declare function foo(cb: () => void): void;

Notes

• The tool only processes .d.ts files.
• It is safe to use on your own type definitions, but always review changes before publishing.

License

MIT