TypeScript Code Typing

Unions & Intersections

Pipe and ampersand types, literal unions, and discriminated shapes

Type-Level Operators

keyof, typeof, infer, conditional types, and mapped keys

satisfies, as const & Bang

Assertion operators, optional marks, and definite assignment

Arrows, Overloads & Predicates

Function-type arrows, overload signatures, and is/asserts guards

Checkpoint: Symbol Fluency

Every TypeScript glyph cluster from this module in one longer drill

Keywords

All reserved words and TypeScript-specific keywords

Declarations

Interfaces, type aliases, generics, and typed functions

Narrowing unknown

typeof, in, instanceof, and Array.isArray instead of any

Utility Types

Omit, Pick, Record, Awaited, and the Exclude/Extract pair

Idiomatic One-Liners

satisfies, mapped types, and utility type expressions

Async Idioms

Promise.all, allSettled, race, and for await loops

Checkpoint: Keywords & Idioms

A Result union with constructors and an exhaustive never check

Control Flow

Type guards, narrowing, and discriminated unions in real branches

Functions & Methods

Generics, overloads, and typed async handlers

Class & Fluent Builder

Parameter properties and this-returning chains

Typed Error Classes

Error subclasses narrowed with instanceof

Maps, Sets & Records

Typed collection work with spreads and reduce

Realistic Snippet

A typed fetch wrapper with a consistent response envelope

Generic Repository

A branded id, a repository interface, and its in-memory implementation

Checkpoint: Real Snippets

A typed event-map emitter with keyed payloads and unsubscribe handles

Speed Run: Runtime Validator

A dependency-free validator returning Result<T, string[]> at full pace

Speed Run: Typed Fetch Client

A generic private send method wrapped by get and post

Speed Run: State Reducer

A cart reducer over a discriminated action union

Speed Run: Utility Type Gymnastics

Recursive mapped types, template literal keys, and Awaited chains

Speed Run: Tests & Asserts

A node:test suite with typed fixtures and strict assertions

Checkpoint: Sustained Speed

A layout leaderboard summarised and formatted in one continuous run

Assessment Sim 1: CSV Record Parser

A complete row-to-record parser that accumulates errors instead of throwing

Assessment Sim 2: Generic TTL Cache

A full expiring cache with typed keys and a load-through helper

Assessment Sim 3: Typed Job Queue

A complete worker loop dispatching a discriminated job union

Assessment Sim 4: Config Loader

A whole env-to-typed-shape loader with guards and range checks

Checkpoint: TypeScript Mastery Final

A typed order-analytics pipeline -- the course's graded final