Mastering Vue 3 Composables: A Comprehensive Style Guide

Core Philosophy

Composables remain functions at their core—leverage established software design principles rather than inventing new patterns.

Key Rules

Naming & Organization

• File naming: Prefix with use, PascalCase (e.g., useCounter.ts)
• Composable naming: Descriptive, intention-revealing (useUserData() not useData())
• Folder structure: Dedicated src/composables/ directory

Arguments & Structure

• Object arguments: Use when passing 4+ parameters for clarity
• Consistent ordering: Refs → Computed → Methods → Lifecycle hooks → Watchers

Design Principles

• Single Responsibility: Each composable has one reason to change
• Separation of Concerns: Manage state/logic only; leave UI operations to components
• Error Handling: Expose error state rather than swallowing errors internally

Composable Anatomy

1. Primary State: Core reactive data
2. Supportive State: Loading, error, status indicators
3. Methods: Functions updating state and calling external services

Functional Core, Imperative Shell

Isolate pure, side-effect-free logic from Vue-specific operations. This pattern improves testability and maintainability significantly.

Related

Part of a Vue 3 best practices series that includes how-to-structure-vue-projects for architecture patterns and vue3-testing-pyramid-vitest-browser-mode for testing composables effectively.