TypeScript Tutorial

Fundamentals

Introduction
What TypeScript is and why it exists Simple Types
The building blocks of TypeScript's type system Special Types
Types that handle edge cases beyond standard values Data Types Overview
How TypeScript categorises every kind of value Variables
How TypeScript governs variable declaration and scope Type Annotations
How to explicitly tell the compiler what a value is Arrays
How TypeScript ensures type safety in ordered collections Tuples
How to model fixed-structure, mixed-type sequences Objects
How TypeScript describes and enforces object shapes

Type System

Type Inference
How the compiler deduces types without annotations Explicit vs Inferred Types
When to annotate and when to let the compiler decide Union Types
How to express values that can be one of several types Intersection Types
How to produce a type that satisfies multiple contracts at once Literal Types
How to restrict a value to one specific, exact type Null & Undefined
How TypeScript handles the absence of a value never Type
The type that represents code that can never be reached unknown Type
How to safely accept any value without losing type safety Type Aliases
How to give a reusable name to any type expression Type Assertions
How to override the compiler's inferred type when you know better Type Guards
How to narrow a type based on runtime checks Type Casting
How to decide between assertions and runtime validation

Object Types & Structures

Introduction
How TypeScript models the shape of structured data Interfaces
How to define a named contract for an object's shape Aliases & Interfaces
How type aliases and interfaces differ and when to choose each Enums
How to define a named set of related constant values Index Signatures
How to type objects whose keys are not known in advance Maps & Sets
How TypeScript types keyed and unique-value collections

Functions

Introduction
How TypeScript applies types to function signatures Arrow Functions
How arrow functions differ from regular functions in TypeScript Function Overloading
How to give one function multiple typed call signatures

Classes & OOP

Classes
How TypeScript extends JavaScript classes with type safety Access Modifiers
How to control what parts of a class are visible to the outside Abstract Classes
How to define a class that must be extended before it can be used Inheritance
How derived classes reuse and extend their parent's behaviour Declaration Merging
How TypeScript combines multiple declarations of the same name Namespaces
How to organise related types and values under a single name

Generics

Introduction
How generics allow one piece of code to work with many types Basic Generics
The foundational generic patterns every TypeScript developer needs Generic Functions
How functions preserve type relationships across their inputs and outputs Generic Classes
How a class can be written once and work with any type Generic Interfaces
How to write a contract that adapts to the type it is given Generic Constraints
How to restrict which types a generic will accept Utility Types
TypeScript's built-in generic types for common transformations keyof Operator
How to turn an object's property names into a type

Advanced Type System

Advanced Types
How TypeScript computes new types from existing ones Conditional Types
How to select a type based on a type-level condition Mapped Types
How to produce a new type by transforming every property of an existing one Decorators
How to attach reusable behaviour to classes and their members

Asynchronous TypeScript

Async Programming
How JavaScript handles operations that take time to complete Promises
How to represent and work with a value that arrives in the future Async/Await
How to write asynchronous code that reads like synchronous code Error Handling
How to deal with failures in a type-safe and structured way

Modules & Project Structure

Modules
How TypeScript organises code across files and boundaries Configuration
How to control every aspect of TypeScript's compilation behaviour Tooling
How to set up the tools that work alongside the TypeScript compiler Compiler API
How to use the TypeScript compiler as a library in your own programs Performance
How to keep large TypeScript projects fast to compile and run

Integration & Ecosystem

Node.js Integration
How TypeScript works with Node.js built-in APIs TypeScript with Node.js
How to build a typed Node.js application from the ground up React Integration
How TypeScript and React work together to type UI components TypeScript with React
How to build a fully typed React application DefinitelyTyped
How to add type safety to JavaScript libraries that ship without types In JS Projects
How to bring TypeScript's benefits to an existing JavaScript codebase

Migration & Best Practices

Migration
How to move an existing JavaScript project to TypeScript incrementally Best Practices
How to write TypeScript that is safe, readable, and maintainable Testing
How to write and type tests for TypeScript code