🎯

module-augmentation

🎯Skill

from marius-townhouse/effective-typescript-skills

What it does

Extends and augments third-party module types by adding properties, methods, and interfaces with type safety.

📦

Part of

marius-townhouse/effective-typescript-skills(83 items)

module-augmentation

Installation

Quick InstallInstall with npx

npx skills add marius-townhouse/effective-typescript-skills --all

Quick InstallInstall with npx

npx skills add marius-townhouse/effective-typescript-skills -s prefer-unknown-over-any exhaustiveness-checking

Quick InstallInstall with npx

npx skills add marius-townhouse/effective-typescript-skills -a opencode claude-code

Quick InstallInstall with npx

npx skills add marius-townhouse/effective-typescript-skills -l

git cloneClone repository

git clone https://github.com/marius-townhouse/effective-typescript-skills.git

📖 Extracted from docs: marius-townhouse/effective-typescript-skills

Need more details? View full documentation on GitHub →

1Installs

AddedFeb 4, 2026

View on GitHub Back to Skills

Skill Details

SKILL.md

Use when extending third-party types. Use when adding properties to existing interfaces. Use when plugins extend core types. Use when declaration merging is needed. Use when augmenting global types.

Overview

# Use Module Augmentation to Improve Types

Overview

Module augmentation allows you to add declarations to existing modules, including third-party libraries. This is useful when a library's types are incomplete or when you're extending a library with plugins. Use declare module to add properties, methods, or types to existing modules.

When to Use This Skill

Extending third-party types
Adding properties to existing interfaces
Plugins that extend core types
Declaration merging needed
Augmenting global types

The Iron Rule

Use module augmentation to add to existing types. Declare the same module name and add your declarations.

Example

```typescript

// Adding to an existing module

// types/vue.d.ts

declare module 'vue' {

export interface ComponentCustomProperties {

$myProperty: string;

$myMethod(): void;

}

// Now Vue components have these properties

// this.$myProperty works with type safety

// Augmenting global types

declare global {

interface Window {

myLib: MyLibrary;

}

// Now window.myLib is typed

```

Reference

Effective TypeScript, 2nd Edition by Dan Vanderkam
Item 71: Use Module Augmentation to Improve Types

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