Effective Typescript

This is the code sample repo for Effective TypeScript: 62 Specific Ways to Improve Your TypeScript. The book is available through:

• O'Reilly
• Amazon

and others. Here are the items with associated code samples:

• Chapter 1: Getting to Know TypeScript

  • 📝 Item 1: Understand the Relationship Between TypeScript and JavaScript
  • 📝 Item 2: Know Which TypeScript Options You’re Using
  • 📝 Item 3: Understand That Code Generation Is Independent of Types
  • 📝 Item 4: Get Comfortable with Structural Typing
  • 📝 Item 5: Limit Use of the any Type

• Chapter 2: TypeScript’s Type System

  • 📝 Item 6: Use Your Editor to Interrogate and Explore the Type System
  • 📝 Item 7: Think of Types as Sets of Values
  • 📝 Item 8: Know How to Tell Whether a Symbol Is in the Type Space or Value Space
  • 📝 Item 9: Prefer Type Declarations to Type Assertions
  • 📝 Item 10: Avoid Object Wrapper Types (String, Number, Boolean, Symbol, BigInt)
  • 📝 Item 11: Recognize the Limits of Excess Property Checking
  • 📝 Item 12: Apply Types to Entire Function Expressions When Possible
  • 📝 Item 13: Know the Differences Between type and interface
  • 📝 Item 14: Use Type Operations and Generics to Avoid Repeating Yourself
  • 📝 Item 15: Use Index Signatures for Dynamic Data
  • 📝 Item 16: Prefer Arrays, Tuples, and ArrayLike to number Index Signatures
  • 📝 Item 17: Use readonly to Avoid Errors Associated with Mutation
  • 📝 Item 18: Use Mapped Types to Keep Values in Sync

• Chapter 3: Type Inference

  • 📝 Item 19: Avoid Cluttering Your Code with Inferable Types
  • 📝 Item 20: Use Different Variables for Different Types
  • 📝 Item 21: Understand Type Widening
  • 📝 Item 22: Understand Type Narrowing
  • 📝 Item 23: Create Objects All at Once
  • 📝 Item 24: Be Consistent in Your Use of Aliases
  • 📝 Item 25: Use async Functions Instead of Callbacks for Asynchronous Code
  • 📝 Item 26: Understand How Context Is Used in Type Inference
  • 📝 Item 27: Use Functional Constructs and Libraries to Help Types Flow

• Chapter 4: Type Design

  • 📝 Item 28: Prefer Types That Always Represent Valid States
  • 📝 Item 29: Be Liberal in What You Accept and Strict in What You Produce
  • 📝 Item 30: Don’t Repeat Type Information in Documentation
  • 📝 Item 31: Push Null Values to the Perimeter of Your Types
  • 📝 Item 32: Prefer Unions of Interfaces to Interfaces of Unions
  • 📝 Item 33: Prefer More Precise Alternatives to String Types
  • 📝 Item 34: Prefer Incomplete Types to Inaccurate Types
  • 📝 Item 35: Generate Types from APIs and Specs, Not Data
  • 📝 Item 36: Name Types Using the Language of Your Problem Domain
  • 📝 Item 37: Consider “Brands” for Nominal Typing

• Chapter 5: Working with any

  • 📝 Item 38: Use the Narrowest Possible Scope for any Types
  • 📝 Item 39: Prefer More Precise Variants of any to Plain any
  • 📝 Item 40: Hide Unsafe Type Assertions in Well-Typed Functions
  • 📝 Item 41: Understand Evolving any
  • 📝 Item 42: Use unknown Instead of any for Values with an Unknown Type
  • 📝 Item 43: Prefer Type-Safe Approaches to Monkey Patching
  • 📝 Item 44: Track Your Type Coverage to Prevent Regressions in Type Safety

• Chapter 6: Types Declarations and @types

  • 📝 Item 45: Put TypeScript and @types in devDependencies
  • 📝 Item 46: Understand the Three Versions Involved in Type Declarations
  • 📝 Item 47: Export All Types That Appear in Public APIs
  • 📝 Item 48: Use TSDoc for API Comments
  • 📝 Item 49: Provide a Type for this in Callbacks
  • 📝 Item 50: Prefer Conditional Types to Overloaded Declarations
  • 📝 Item 51: Mirror Types to Sever Dependencies
  • 📝 Item 52: Be Aware of the Pitfalls of Testing Types

• Chapter 7: Writing and Running Your Code

  • 📝 Item 53: Prefer ECMAScript Features to TypeScript Features
  • 📝 Item 54: Know How to Iterate Over Objects
  • 📝 Item 55: Understand the DOM hierarchy
  • 📝 Item 56: Don’t Rely on Private to Hide Information
  • 📝 Item 57: Use Source Maps to Debug TypeScript

• Chapter 8. Migrating to TypeScript

  • 📝 Item 58: Write Modern JavaScript
  • 📝 Item 59: Use @ts-check and JSDoc to Experiment with TypeScript
  • 📝 Item 60: Use allowJs to Mix TypeScript and JavaScript
  • 📝 Item 61: Convert Module by Module Up Your Dependency Graph
  • 📝 Item 62: Don’t Consider Migration Complete Until You Enable noImplicitAny