JavaScript and TypeScript Best Practices
Comprehensive coding standards for JavaScript and TypeScript applications, designed for AI agents and LLMs working with modern JavaScript/TypeScript codebases.
Note: This skill focuses on general best practices, TypeScript patterns, and safety. For performance optimization, use the accelint-ts-performance skill instead.
When to Use This Skill
This skill provides expert-level patterns for JavaScript and TypeScript code. Load AGENTS.md to scan rule summaries and identify relevant optimizations for your task.
How to Use
This skill uses a progressive disclosure structure to minimize context usage:
1. Start with the Overview (AGENTS.md)
Read AGENTS.md for a concise overview of all rules with one-line summaries organized by category.
2. Load Specific Rules as Needed
When you identify a relevant pattern or issue, load the corresponding reference file for detailed implementation guidance:
Quick Start:
- quick-start.md - Complete workflow examples with before/after code
General Best Practices:
- naming-conventions.md - Descriptive names, qualifier ordering, boolean prefixes
- functions.md - Function size, parameters, explicit values
- control-flow.md - Early returns, flat structure, block style
- state-management.md - const vs let, immutability, pure functions
- return-values.md - Return zero values instead of null/undefined
- misc.md - Line endings, defensive programming, technical debt
- code-duplication.md - Extract common patterns, DRY principle, when to consolidate
TypeScript:
- any.md - Avoid any, use unknown or generics
- enums.md - Use as const objects instead of enum
- type-vs-interface.md - Prefer type over interface
Safety:
- input-validation.md - Validate external data with schemas
- assertions.md - Split assertions, include values
- error-handling.md - Handle all errors explicitly
- error-messages.md - User-friendly vs developer-specific messages
Performance:
- For performance optimization tasks, use the
accelint-ts-performanceskill for comprehensive profiling workflows and optimization patterns
Documentation:
- For documentation tasks, use the
accelint-ts-documentationskill for comprehensive JSDoc and comment guidance
3. Apply the Pattern
Each reference file contains:
- ❌ Incorrect examples showing the anti-pattern
- ✅ Correct examples showing the optimal implementation
- Explanations of why the pattern matters
4. Use the Report Template
When this skill is invoked, use the standardized report format:
Template: assets/output-report-template.md
The report format provides:
- Executive Summary with impact assessment
- Severity levels (Critical, High, Medium, Low) for prioritization
- Impact analysis (potential bugs, type safety, maintainability, runtime failures)
- Categorization (Type Safety, Safety, State Management, Return Values, Code Quality)
- Pattern references linking to detailed guidance in references/
- Phase 2 summary table for tracking all issues
When to use the audit template:
- Skill invoked directly via
/accelint-ts-best-practices <path> - User asks to "review code quality" or "audit code" across file(s), invoking skill implicitly
When NOT to use the report template:
- User asks to "fix this type error" (direct implementation)
- User asks "what's wrong with this code?" (answer the question)
- User requests specific fixes (apply fixes directly without formal report)