TypeScript

Introduction to TypeScript

What TypeScript is, why teams adopt it, how compilation works, installing tsc, and your first typed program.

Simple & Special Types

string, number, boolean, bigint, type inference, explicit vs implicit typing, and the special types any, unknown, never, void, null and undefined.

Arrays & Tuples

Typed arrays, readonly arrays, array methods with types, tuples for fixed-length data, named and optional tuple elements, and destructuring.

Object Types & Type Aliases

Describing object shapes inline, optional and readonly properties, index signatures, type aliases, and excess property checks.

Interfaces

Declaring object contracts with interface, extending interfaces, declaration merging, interfaces for functions, and when to use interface vs type.

Enums & Literal Types

Numeric and string enums, const enums, literal types and as const as lighter alternatives, and choosing between them.

Union, Intersection & Literal Types

Combining types with | and &, literal types, discriminated unions, and exhaustive checks with never.

Functions & Types

Typing parameters and return values, optional, default and rest parameters, function type aliases, callbacks, and overloads.

Type Narrowing & Casting

typeof, instanceof, in, equality and truthiness narrowing, type predicates, assertion functions, and casting with as — plus when casting is dangerous.

Classes & Access Modifiers

Typed class properties, constructors and parameter properties, public/private/protected, readonly, getters/setters, implements, inheritance and abstract classes.

Generics

Writing reusable type-safe functions, interfaces and classes with type parameters, constraints with extends, defaults, and generic utility patterns.

Utility Types

The built-in type helpers — Partial, Required, Readonly, Pick, Omit, Record, Exclude, Extract, NonNullable, ReturnType, Parameters and Awaited — with real use cases.

keyof, typeof, Indexed & Mapped Types

Getting keys with keyof, types from values with typeof, indexed access types, mapped types, template literal types, and conditional types in practice.

Null, Undefined & Strict Mode

strictNullChecks, optional chaining, nullish coalescing, the non-null assertion, definite assignment, and handling missing data safely.

Modules, tsconfig & Declaration Files

import/export with types, type-only imports, tsconfig.json essentials, declaration files (.d.ts), DefinitelyTyped (@types), and typing JavaScript libraries.

TypeScript in Real Projects

Typing async code and API calls, runtime validation with zod, TypeScript with React and Node/Express, migrating JavaScript, linting, and team best practices.