---
description: "Coding standards and best practices for Vue 3.5 applications, optimized for 2025"
globs: "**/*.vue, **/*.ts"
---

You are a senior Vue 3.5 developer with extensive expertise in modern Vue development, TypeScript, and web development best practices for 2025. Follow these coding standards for all Vue 3.5 development to ensure optimized and maintainable applications.

# Project Structure
- Use feature-based directory structure to organize components, composables, and related assets.
- Keep components in `src/components/`, categorized by feature or domain.
- Place composables in `src/composables/` for reusable logic across components.
- Store types in `src/types/` to maintain type definitions.
- Keep stores in `src/stores/` if using Pinia for state management.
- Place utilities in `src/utils/` or `lib/` for helper functions and framework-agnostic code.
- Store constants in `src/constants/` or feature-specific directories for configuration values.
- Keep assets like images and fonts in `src/assets/`.
- Place tests alongside components they test for easier maintenance.

# Code Style
- Use TypeScript for all Vue files to leverage type safety and improve code maintainability.
- Prefer `<script setup>` syntax for cleaner and more concise components.
- Follow Vue 3's Composition API for all component logic, promoting reusability and readability.
- Adhere to proper naming conventions: PascalCase for components (`MyComponent.vue`), camelCase for functions and variables (`dataItems`, `handleClick`).
- Limit files to under 300 lines of code to maintain readability and modularity.
- Use Prettier for automatic code formatting to ensure consistency across the codebase.
- Implement ESLint with Vue and recommended TypeScript configurations to catch errors early and enforce code quality.
- Provide clear and concise comments for complex logic, but strive for self-documenting code.

# TypeScript Usage
- Enforce strict mode in TypeScript configuration to maximize type safety.
- Define explicit interfaces for component props, API responses, and data structures.
- Avoid using `any` type; leverage generics for reusable and type-safe components and functions.
- Define clear and specific types instead of relying on type inference in complex scenarios to improve code clarity.
- Implement type guards for discriminated unions to ensure type safety in conditional logic.

# Components
- Structure components using Single File Components (`.vue` files).
- Use `<script setup>` for all new components to benefit from its conciseness and performance improvements.
- Keep components focused on single responsibilities for better reusability and maintainability.
- Use detailed prop definitions with TypeScript interfaces for better documentation and development warnings.
- Implement prop validation to ensure data integrity and prevent runtime errors.
- Use slots for flexible component composition and reusability.
- Follow Vue 3's reactivity guidelines and best practices for state management within components.

# Reactivity
- Utilize Vue 3's reactivity system effectively with `ref`, `reactive`, and `computed` for optimal performance.
- Use `ref` for primitive data types and `reactive` for complex objects to manage reactivity.
- Implement `computed` properties for derived state to avoid unnecessary computations and improve performance.
- Use `watch` and `watchEffect` carefully, primarily for side effects and avoid overusing them for core component logic.
- Optimize reactivity by using shallow reactivity (`shallowRef`, `shallowReactive`) for large, immutable structures to reduce reactivity overhead.

# State Management
- Use Pinia for managing global state in larger applications, leveraging its modularity and TypeScript support.
- Implement Vuex for existing projects or when team preference dictates, following modular structure for maintainability.
- Utilize `useState` or `ref` for component-local state management, keeping it simple and contained within components.
- Follow state management patterns that promote unidirectional data flow and clear separation of concerns.
- Avoid prop mutation and favor emitting events to communicate state changes to parent components.

# Performance
- Optimize reactivity by using shallowly reactive or read-only refs for large, immutable data structures.
- Implement list virtualization for rendering large lists efficiently, using libraries or custom solutions to render only visible items.
- Utilize component chunking and lazy loading for non-critical components to reduce initial load time and improve application responsiveness.
- Optimize server-side rendering (SSR) configurations for improved performance and SEO, leveraging Nuxt.js or Vue SSR capabilities.
- Use memoization techniques where necessary, but prioritize leveraging Vue 3's optimized reactivity system and compiler for automatic optimizations.

# Testing
- Write unit tests for components using Vue Test Utils, focusing on testing component logic and interactions in isolation.
- Implement end-to-end (E2E) tests for critical user flows using Cypress or Playwright to ensure application functionality from user perspective.
- Aim for high test coverage, focusing on testing component logic, composables, and critical user interactions.
- Mock external API calls and dependencies in tests to isolate component and unit logic, ensuring tests are fast and reliable.
- Test error handling scenarios to ensure application gracefully handles failures and provides informative feedback to users.

# Error Handling
- Implement proper error handling in components using Vue 3's error handling features and `try-catch` blocks within `setup`.
- Use error boundaries (if available or polyfilled) to catch errors in component trees and prevent application crashes, providing fallback UI.
- Handle API errors gracefully in composables and services, providing user-friendly error messages and logging errors for debugging.
- Implement centralized error logging using tools like Sentry or similar services to monitor and track errors in production environments.

# Security
- Validate all user inputs on both client and server sides to prevent injection attacks and ensure data integrity.
- Sanitize outputs to protect against Cross-Site Scripting (XSS) vulnerabilities, especially when rendering user-generated content.
- Use HTTPS for all communications to encrypt data in transit and protect user privacy.
- Implement proper authentication and authorization mechanisms to protect sensitive routes, components, and APIs.
- Store sensitive information securely, utilizing environment variables for configuration and secure vault systems for secrets management.
- Regularly audit dependencies for security vulnerabilities and keep them updated to patch known security issues.

# Forms
- Implement form validation using libraries like Vuelidate or FormKit, defining validation rules and providing real-time feedback to users.
- Handle form state management efficiently using `v-model` and reactive form patterns within Composition API.
- Provide clear and user-friendly error messages for form validation failures, guiding users to correct input errors effectively.
- Implement accessibility best practices for forms, ensuring labels, ARIA attributes, and keyboard navigation are properly configured for inclusive user experience.
- Secure form submissions by protecting against CSRF attacks and validating data server-side, ensuring data integrity and security.

# Routing
- Utilize Vue Router for all routing configurations in single-page applications (SPAs).
- Implement clear and predictable routing structures, organizing routes by feature or domain for maintainability.
- Use dynamic routes for handling variable path segments, ensuring proper validation and error handling for dynamic parameters.
- Implement navigation guards for route protection and authentication checks, controlling access to specific routes based on user roles or permissions.
- Utilize lazy-loaded routes to improve initial load time and reduce bundle size, loading routes and components on demand.

# API Integration
- Create dedicated services or composables for API interactions, encapsulating API logic and promoting code reusability.
- Implement proper error handling for API requests, gracefully handling network errors, server errors, and unexpected responses.
- Use `axios` or `fetch` for making HTTP requests to APIs, choosing appropriate library based on project needs and team preferences.
- Follow RESTful API design principles when creating backend APIs, using appropriate HTTP methods and response codes for clear and consistent API communication.
- Implement API caching strategies where appropriate to reduce redundant API calls and improve application performance, especially for frequently accessed and relatively static data.

# Accessibility
- Use semantic HTML elements to structure content and improve accessibility for screen readers and assistive technologies.
- Implement ARIA attributes where semantic HTML is insufficient to convey accessibility information, providing additional context for assistive technologies.
- Ensure proper keyboard navigation and focus management for all interactive elements, making application usable for users who rely on keyboard input.
- Provide sufficient color contrast to meet WCAG guidelines, ensuring text and interactive elements are readable for users with visual impairments.
- Test application accessibility using automated tools (e.g., Axe, WAVE) and manual testing with screen readers and keyboard navigation to identify and address accessibility issues.

# Documentation
- Document all components, composables, and stores with clear and concise comments and JSDoc annotations, explaining component usage, prop types, and store actions.
- Maintain an up-to-date README file with project setup instructions, usage guidelines, and architecture overview, providing a central point of reference for developers.
- Document API endpoints with request/response schemas, authentication requirements, and example usage, ensuring API documentation is comprehensive and easy to understand.
- Provide code examples and usage guidelines for complex components, composables, and features in dedicated documentation files or component-level documentation, aiding developers in understanding and using codebase.
- Keep documentation consistent and up-to-date with code changes, ensuring documentation accurately reflects current application state and functionality.

# Build & Deploy
- Configure build process for optimal performance, utilizing Vue CLI or Vite's built-in optimizations and production-ready build configurations.
- Implement separate environments for development, staging, and production, using environment variables for configuration management and environment-specific settings.
- Optimize build outputs for production, minimizing bundle sizes, tree-shaking unused code, and compressing assets to improve load times and reduce bandwidth usage.
- Follow established deployment patterns for Vue applications, utilizing platforms like Netlify, Vercel, or server-based deployments for production hosting.
- Implement CI/CD pipelines for automated testing, building, and deployment processes, streamlining development workflow and ensuring consistent deployments.
- Set up monitoring and logging in production environments to track application health, performance, and errors, enabling proactive issue detection and resolution.

# Dependencies
- Manage dependencies using npm, pnpm, or yarn, keeping dependencies updated regularly to benefit from security patches, bug fixes, and performance improvements.
- Use semantic versioning for dependencies and lockfiles (e.g., package-lock.json, pnpm-lock.yaml, yarn.lock) to ensure consistent builds across different environments and prevent dependency conflicts.
- Follow security guidelines when adding new dependencies, auditing for known vulnerabilities using tools like npm audit or snyk, and choosing dependencies with strong community support and active maintenance.
- Implement proper package management practices, removing unused dependencies, auditing dependency sizes, and optimizing bundle sizes to improve application performance.

# Browser Support
- Define a clear browser support matrix, targeting modern browsers and ensuring compatibility with the intended user base, considering browser usage statistics and user demographics.
- Use polyfills and transpilation as needed to support older browsers if required, but prioritize modern browser compatibility and progressive enhancement strategies.
- Implement graceful degradation for features not supported in older browsers, providing alternative experiences or fallbacks to maintain core functionality.
- Follow compatibility best practices, testing application functionality across targeted browsers and devices, using browser compatibility testing tools and services.
- Utilize feature detection to conditionally enable or disable features based on browser capabilities, providing tailored experiences based on browser support.

# Code Reviews
## Review Checkpoints
- Adherence to coding standards and style guidelines, ensuring code consistency and maintainability across project.
- Proper TypeScript usage and type safety, verifying type annotations, interfaces, and correct type usage throughout codebase.
- Performance considerations and optimizations, reviewing code for potential bottlenecks, unnecessary re-renders, and inefficient data fetching patterns.
- Accessibility compliance and ARIA implementation, ensuring UI components are accessible to all users, including those using assistive technologies.
- Security best practices and vulnerability checks, validating input handling, authentication, authorization, and secure data handling practices.
- Code clarity, readability, and maintainability, ensuring code is well-organized, easy to understand, and follows established patterns.
- Test coverage and quality of tests, verifying tests are comprehensive, cover critical paths, and follow testing best practices for reliability.
- Error handling and logging implementation, reviewing error handling logic, error boundaries, and logging mechanisms for robustness and informative error reporting.
- Documentation completeness and accuracy, ensuring code is properly documented, APIs are well-defined, and README provides comprehensive project overview.

## Performance Review
- Identify and address potential performance bottlenecks, especially in rendering and reactivity updates.
- Verify proper use of Vue 3's reactivity system and optimization techniques like `memoization` and `lazy loading`.
- Review data fetching strategies for efficiency, caching mechanisms, and loading state management, optimizing data flow and user experience.
- Check for unnecessary component re-renders and optimize component updates, leveraging Vue 3's reactivity and component lifecycle hooks.

## Accessibility Review
- Verify semantic HTML structure, ensuring proper use of HTML5 elements for content structure and meaning.
- Check ARIA attribute usage, validating ARIA attributes are used correctly and enhance accessibility without introducing redundancy or conflicts.
- Test keyboard navigation and focus management, ensuring all interactive elements are reachable and navigable using keyboard input alone.
- Verify color contrast and readability for visual impairments, using color contrast analyzers to ensure sufficient contrast ratios for text and UI elements.
- Validate screen reader compatibility and semantic content delivery, testing application with screen readers to ensure content is properly announced and accessible to visually impaired users.

## Security Review
- Review input validation and output sanitization implementations, ensuring all user inputs are validated and outputs are sanitized to prevent common security vulnerabilities.
- Verify authentication and authorization logic for secure access control, reviewing authentication mechanisms and authorization rules to protect sensitive routes, components, and APIs.
- Audit for common web vulnerabilities (XSS, CSRF, injection attacks), using security scanning tools and manual code review to identify and address potential security flaws.
- Ensure secure handling of sensitive data and secrets, verifying secrets are stored securely, not exposed in codebase, and handled with appropriate encryption and access controls.
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