How to use
- Copy the installation command and review the source package before installing it in your own agent environment.
- Check the source document for required tools, credentials and supported hosts.
- Describe your input and desired deliverable; review the output against the source material.
npx skills add https://github.com/pymodel/react-frontend-skills --skill typescriptBefore you start
- Installation does not include a model subscription, API allowance or permission to access your files.
- Repository stars and installation counts describe activity, not an independent quality or security test.
Original skill document
Rendered from the source repository. Headings, examples, code, tables, links, and referenced images are preserved.
TypeScript Best Practices
Comprehensive TypeScript 7-compatible guide with 44 rules across 8 categories, covering compiler configuration, type-system performance, async code, modules, safety, and measured runtime optimization.
When to Apply
Reference these guidelines when:
- Configuring tsconfig.json for a new or existing project
- Writing complex type definitions or generics
- Optimizing async/await patterns and data fetching
- Organizing modules and managing imports
- Reviewing code for compilation or runtime performance
Rule Categories by Priority
| Priority | Category | Impact | Prefix |
|---|---|---|---|
| 1 | Type System Performance | CRITICAL | type- |
| 2 | Compiler Configuration | CRITICAL | tscfg- |
| 3 | Async Patterns | HIGH | async- |
| 4 | Module Organization | HIGH | module- |
| 5 | Type Safety Patterns | MEDIUM-HIGH | safety- |
| 6 | Memory Management | MEDIUM | mem- |
| 7 | Runtime Optimization | LOW-MEDIUM | runtime- |
| 8 | Advanced Patterns | LOW | advanced- |
Table of Contents
- Type System Performance — CRITICAL
- 1.1 Add Explicit Return Types to Exported Functions — CRITICAL (faster declaration emit)
- 1.2 Avoid Deeply Nested Generic Types — CRITICAL (prevents exponential instantiation cost)
- 1.3 Avoid Large Union Types — CRITICAL (quadratic O(n²) comparison cost)
- 1.4 Extract Conditional Types to Named Aliases — CRITICAL (enables compiler caching, prevents re-evaluation)
- 1.5 Limit Type Recursion Depth — CRITICAL (prevents exponential type expansion)
- 1.6 Prefer Interfaces Over Type Intersections — CRITICAL (faster type resolution)
- 1.7 Simplify Complex Mapped Types — CRITICAL (reduces type computation)
- Compiler Configuration — CRITICAL
- 2.1 Configure Include and Exclude Properly — CRITICAL (prevents scanning thousands of unnecessary files)
- 2.2 Enable Incremental Compilation — CRITICAL (faster rebuilds)
- 2.3 Choose skipLibCheck Deliberately — CRITICAL (faster compilation)
- 2.4 Enable strictFunctionTypes for Sound Function Assignments — CRITICAL (enables optimized variance checking)
- 2.5 Use isolatedModules for Single-File Transpilers — CRITICAL (faster transpilation with bundlers)
- 2.6 Use Project References for Large Codebases — CRITICAL (faster incremental builds)
- 2.7 Migrate TypeScript 7 Configuration Deliberately — CRITICAL
- Async Patterns — HIGH
- 3.1 Annotate Async Function Return Types — HIGH (prevents runtime errors, improves inference)
- 3.2 Avoid await Inside Loops — HIGH (scales linearly with the number of iterations)
- 3.3 Avoid Unnecessary async/await — HIGH (eliminates microtask queue overhead)
- 3.4 Defer await Until Value Is Needed — HIGH (enables implicit parallelization)
- 3.5 Use Promise.all for Independent Operations — HIGH (improvement in I/O-bound code)
- Module Organization — HIGH
- 4.1 Avoid Barrel File Imports — HIGH (import cost, larger bundles)
- 4.2 Avoid Circular Dependencies — HIGH (prevents runtime undefined errors and slow compilation)
- 4.3 Control @types Package Inclusion — HIGH (prevents type conflicts and reduces memory usage)
- 4.4 Use Dynamic Imports for Large Modules — HIGH (reduces initial bundle)
- 4.5 Use Type-Only Imports for Types — HIGH (eliminates runtime imports for type information)
- Type Safety Patterns — MEDIUM-HIGH
- 5.1 Enable strictNullChecks — MEDIUM-HIGH
- 5.2 Prefer unknown Over any — MEDIUM-HIGH
- 5.3 Use Assertion Functions for Validation — MEDIUM-HIGH
- 5.4 Use const Assertions for Literal Types — MEDIUM-HIGH
- 5.5 Use Exhaustive Checks for Union Types — MEDIUM-HIGH
- 5.6 Use Type Guards for Runtime Type Checking — MEDIUM-HIGH
- Memory Management — MEDIUM
- 6.1 Avoid Closure Memory Leaks — MEDIUM (prevents retained references in long-lived callbacks)
- 6.2 Avoid Global State Accumulation — MEDIUM (prevents unbounded memory growth)
- 6.3 Clean Up Event Listeners — MEDIUM (prevents unbounded memory growth)
- 6.4 Clear Timers and Intervals — MEDIUM (prevents callback retention and repeated execution)
- 6.5 Use WeakMap for Object Metadata — MEDIUM (prevents memory leaks, enables automatic cleanup)
- Runtime Optimization — LOW-MEDIUM
- 7.1 Avoid Object Spread in Hot Loops — LOW-MEDIUM
- 7.2 Hoist Loop-Invariant Work in Measured Hot Paths — LOW-MEDIUM
- 7.3 Prefer Native Array Methods Over Lodash — LOW-MEDIUM
- 7.4 Use for-of for Simple Iteration — LOW-MEDIUM
- 7.5 Use Modern String Methods — LOW-MEDIUM
- 7.6 Use Set/Map for O(1) Lookups — LOW-MEDIUM
- Advanced Patterns — LOW
- 8.1 Use Branded Types for Type-Safe IDs — LOW (prevents mixing incompatible ID types)
- 8.2 Use satisfies for Type Validation with Inference — LOW (prevents property access errors, enables reliable autocomplete)
- 8.3 Use Template Literal Types for String Patterns — LOW (prevents string format errors at compile time)
