Tackling TypeScript

I Preliminaries
	About this book
		Where is the homepage of this book?
		What is in this book?
		What do I get for my money?
		How can I preview the content?
		How do I report errors?
		What do the notes with icons mean?
		Acknowledgements
	Why TypeScript?
		The benefits of using TypeScript
		The downsides of using TypeScript
		TypeScript myths
	Free resources on TypeScript
II Getting started with TypeScript
	How does TypeScript work? The bird's eye view
		The structure of TypeScript projects
		Programming TypeScript via an integrated development environment (IDE)
		Other files produced by the TypeScript compiler
		Using the TypeScript compiler for plain JavaScript files
	Trying out TypeScript
		The TypeScript Playground
		TS Node
	Notation used in this book
		Test assertions (dynamic)
		Type assertions (static)
	The essentials of TypeScript
		What you'll learn
		Specifying the comprehensiveness of type checking
		Types in TypeScript
		Type annotations
		Type inference
		Specifying types via type expressions
		The two language levels: dynamic vs. static
		Type aliases
		Typing Arrays
		Function types
		Union types
		Optional vs. default value vs. undefined|T
		Typing objects
		Type variables and generic types
		Example: a type-parameterized class
		Conclusion: understanding the initial example
	Creating CommonJS-based npm packages via TypeScript
		Required knowledge
		Limitations
		The repository ts-demo-npm-cjs
		.gitignore
		.npmignore
		package.json
		tsconfig.json
		TypeScript code
	Creating web apps via TypeScript and webpack
		Required knowledge
		Limitations
		The repository ts-demo-webpack
		package.json
		webpack.config.js
		tsconfig.json
		index.html
		main.ts
		Installing, building and running the web app
		Using webpack without a loader: webpack-no-loader.config.js
	Strategies for migrating to TypeScript
		Three strategies
		Strategy: mixed JavaScript/TypeScript code bases
		Strategy: adding type information to plain JavaScript files
		Strategy: migrating large projects by snapshot testing the TypeScript errors
		Conclusion
III Digging deeper
	What is a type in TypeScript? Two perspectives
		Three questions for each perspective
		Perspective 1: types are sets of values
		Perspective 2: type compatibility relationships
		Nominal type systems vs. structural type systems
		Further reading
	TypeScript enums: How do they work? What can they be used for?
		The basics
		Specifying enum member values (advanced)
		Downsides of numeric enums
		Use cases for enums
		Enums at runtime
		const enums
		Enums at compile time
		Acknowledgment
	Alternatives to enums in TypeScript
		Unions of singleton values
		Discriminated unions
		Object literals as enums
		Enum pattern
		Summary of enums and enum alternatives
		Acknowledgement
	Adding special values to types
		Adding special values in band
		Adding special values out of band
	Typing objects
		Roles played by objects
		Types for objects
		Object vs. object in TypeScript
		Object type literals and interfaces
		Type inference
		Other features of interfaces
		JavaScript's prototype chains and TypeScript's types
		Sources of this chapter
	Class definitions in TypeScript
		Cheat sheet: classes in plain JavaScript
		Non-public data slots in TypeScript
		Private constructors
		Initializing instance properties
		Abstract classes
	Class-related types
		The two prototype chains of classes
		Interfaces for instances of classes
		Interfaces for classes
		Classes as types
		Further reading
	Types for classes as values
		Types for specific classes
		The type operator typeof
		A generic type for classes: Class
	Typing Arrays
		Roles of Arrays
		Ways of typing Arrays
		Pitfall: type inference doesn't always get Array types right
		Pitfall: TypeScript assumes indices are never out of bounds
	Typing functions
		Defining statically typed functions
		Types for functions
		Parameters
		Overloading (advanced)
		Assignability (advanced)
		Further reading and sources of this chapter
IV Dealing with ambiguous types
	The top types any and unknown
		TypeScript's two top types
		The top type any
		The top type unknown
	Type assertions (related to casting)
		Type assertions
		Constructs related to type assertions
	Type guards and assertion functions
		When are static types too general?
		Narrowing via built-in type guards
		User-defined type guards
		Assertion functions
		Quick reference: user-defined type guards and assertion functions
		Alternatives to assertion functions
		@hqoss/guards: library with type guards
	Validating external data
		JSON schema
		Approaches for data validation in TypeScript
		Example: validating data via the library Zod
		Conclusion