TypeScript from Zero

Learn TypeScript from zero, no JavaScript needed: Node.js and TypeScript setup, variables, numbers, strings, types, and a typed task tracker project.

Part 1

TypeScript from Zero: Setup and Your First Program

Install Node.js and TypeScript, run your first program with node, and see why tsc catches mistakes before they run.

typescriptnodebeginnerstsc

Part 2

TypeScript from Zero: Variables with let and const

let for values that change, const for values that stay, and how TypeScript remembers each variable's type.

typescriptvariablesletconst

Part 3

TypeScript from Zero: Numbers and Math

Operators, the Math helpers, the 0.1 + 0.2 surprise and NaN in TypeScript, plus a typo caught by tsc.

typescriptnumbersmathnan

Part 4

TypeScript from Zero: Strings

Quotes, string helpers, template literals and the 5 + 3 trap in TypeScript, caught by tsc.

typescriptstringstemplate literals

Part 5

TypeScript Booleans and Comparisons: === vs ==

TypeScript from Zero, episode 5: TypeScript Booleans and Comparisons: === vs ==. Full code and real outputs, step by step.

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Part 6

TypeScript if, else and switch: Decisions for Beginners

TypeScript from Zero, episode 6: TypeScript if, else and switch: Decisions for Beginners. Full code and real outputs, step by step.

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Part 7

TypeScript Loops: for, while and for...of (and How to Stop an Infinite Loop)

TypeScript from Zero, episode 7: TypeScript Loops: for, while and for...of (and How to Stop an Infinite Loop). Full code and real outputs, step by step.

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Part 8

TypeScript Arrays: Index, push, pop and length

TypeScript from Zero, episode 8: TypeScript Arrays: Index, push, pop and length. Full code and real outputs, step by step.

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Part 9

TypeScript Objects: Properties, Dot vs Brackets (and a Missing Property Error)

TypeScript from Zero, episode 9: TypeScript Objects: Properties, Dot vs Brackets (and a Missing Property Error). Full code and real outputs, step by step.

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Part 10

TypeScript Functions: Parameters, Return and Arrow Functions

TypeScript from Zero, episode 10: TypeScript Functions: Parameters, Return and Arrow Functions. Full code and real outputs, step by step.

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Part 11

TypeScript Project Setup: npm init, tsconfig.json and tsc Explained

TypeScript from Zero, episode 11: TypeScript Project Setup: npm init, tsconfig.json and tsc Explained. Full code and real outputs, step by step.

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Part 12

TypeScript Reading Input: process.argv, readline and @types/node

TypeScript from Zero, episode 12: TypeScript Reading Input: process.argv, readline and @types/node. Full code and real outputs, step by step.

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Part 13

TypeScript Type Annotations vs Inference, Arrays and Tuples

TypeScript from Zero, episode 13: TypeScript Type Annotations vs Inference, Arrays and Tuples. Full code and real outputs, step by step.

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Part 14

TypeScript Function Types: Optional, Default and Rest Parameters, void and never

TypeScript from Zero, episode 14: TypeScript Function Types: Optional, Default and Rest Parameters, void and never. Full code and real outputs, step by step.

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Part 15

TypeScript type vs interface: Optional and readonly Properties

TypeScript from Zero, episode 15: TypeScript type vs interface: Optional and readonly Properties. Full code and real outputs, step by step.

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Part 16

TypeScript Union Types and Narrowing: typeof, in and Array.isArray

TypeScript from Zero, episode 16: TypeScript Union Types and Narrowing: typeof, in and Array.isArray. Full code and real outputs, step by step.

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Part 17

TypeScript null and undefined: Optional Chaining ?. , ?? and the ! Trap

TypeScript from Zero, episode 17: TypeScript null and undefined: Optional Chaining ?. , ?? and the ! Trap. Full code and real outputs, step by step.

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Part 18

TypeScript Literal Types, as const and Why Node Rejects enum

TypeScript from Zero, episode 18: TypeScript Literal Types, as const and Why Node Rejects enum. Full code and real outputs, step by step.

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Part 19

TypeScript Discriminated Unions and Exhaustive switch with never

TypeScript from Zero, episode 19: TypeScript Discriminated Unions and Exhaustive switch with never. Full code and real outputs, step by step.

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Part 20

TypeScript any vs unknown, Type Assertions (as) and satisfies

TypeScript from Zero, episode 20: TypeScript any vs unknown, Type Assertions (as) and satisfies. Full code and real outputs, step by step.

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Part 21

TypeScript Generics for Beginners: Generic Functions and extends Constraints

TypeScript from Zero, episode 21: TypeScript Generics for Beginners: Generic Functions and extends Constraints. Full code and real outputs, step by step.

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Part 22

TypeScript Generic Types and Interfaces: Defaults and a Typed Result Type

TypeScript from Zero, episode 22: TypeScript Generic Types and Interfaces: Defaults and a Typed Result Type. Full code and real outputs, step by step.

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Part 23

TypeScript Classes for Beginners: constructor, #private, implements, abstract

TypeScript from Zero, episode 23: TypeScript Classes for Beginners: constructor, #private, implements, abstract. Full code and real outputs, step by step.

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Part 24

TypeScript Modules: import, export, import type and File Extensions

TypeScript from Zero, episode 24: TypeScript Modules: import, export, import type and File Extensions. Full code and real outputs, step by step.

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Part 25

TypeScript Async Await for Beginners: setTimeout, Promises and the Forgotten await

TypeScript from Zero, episode 25: TypeScript Async Await for Beginners: setTimeout, Promises and the Forgotten await. Full code and real outputs, step by step.

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Part 26

TypeScript Project: Task Tracker CLI, Project Setup and a Discriminated Union Model

TypeScript from Zero, episode 26: TypeScript Project: Task Tracker CLI, Project Setup and a Discriminated Union Model. Full code and real outputs, step by step.

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Part 27

TypeScript CLI: Parsing Arguments with node:util parseArgs and Narrowing the Result

TypeScript from Zero, episode 27: TypeScript CLI: Parsing Arguments with node:util parseArgs and Narrowing the Result. Full code and real outputs, step by step.

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Part 28

TypeScript: Save and Load a JSON File with node:fs/promises (readFile, writeFile)

TypeScript from Zero, episode 28: TypeScript: Save and Load a JSON File with node:fs/promises (readFile, writeFile). Full code and real outputs, step by step.

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Part 29

TypeScript: JSON.parse Returns any - Use unknown and a Type Guard (value is Task)

TypeScript from Zero, episode 29: TypeScript: JSON.parse Returns any - Use unknown and a Type Guard (value is Task). Full code and real outputs, step by step.

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Part 30

TypeScript Error Handling: try/catch with unknown, Custom Errors and Error.cause

TypeScript from Zero, episode 30: TypeScript Error Handling: try/catch with unknown, Custom Errors and Error.cause. Full code and real outputs, step by step.

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Part 31

TypeScript map, filter, reduce, Object.entries, Record and Map for Beginners

TypeScript from Zero, episode 31: TypeScript map, filter, reduce, Object.entries, Record and Map for Beginners. Full code and real outputs, step by step.

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Part 32

TypeScript Utility Types: Partial, Pick, Omit, Required, Readonly, ReturnType

TypeScript from Zero, episode 32: TypeScript Utility Types: Partial, Pick, Omit, Required, Readonly, ReturnType. Full code and real outputs, step by step.

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Part 33

TypeScript: Build a CLI with tsc, the bin Field and npm link (Shebang Included)

TypeScript from Zero, episode 33: TypeScript: Build a CLI with tsc, the bin Field and npm link (Shebang Included). Full code and real outputs, step by step.

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Part 34

TypeScript Zod 4 for Beginners: Schema, z.infer, safeParse and Readable Errors

TypeScript from Zero, episode 34: TypeScript Zod 4 for Beginners: Schema, z.infer, safeParse and Readable Errors. Full code and real outputs, step by step.

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Part 35

TypeScript: Typed Config from process.env with Zod (Fail Fast, Defaults, --env-file)

TypeScript from Zero, episode 35: TypeScript: Typed Config from process.env with Zod (Fail Fast, Defaults, --env-file). Full code and real outputs, step by step.

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Part 36

TypeScript HTTP API with node:http: Routes, Typed JSON Helper, 404 and --watch

TypeScript from Zero, episode 36: TypeScript HTTP API with node:http: Routes, Typed JSON Helper, 404 and --watch. Full code and real outputs, step by step.

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Part 37

TypeScript API: Validate Request Bodies with Zod and Return 422 with Field Errors

TypeScript from Zero, episode 37: TypeScript API: Validate Request Bodies with Zod and Return 422 with Field Errors. Full code and real outputs, step by step.

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Part 38

TypeScript fetch: Typed JSON Client with Zod, POST and AbortController Timeouts

TypeScript from Zero, episode 38: TypeScript fetch: Typed JSON Client with Zod, POST and AbortController Timeouts. Full code and real outputs, step by step.

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Part 39

TypeScript EventEmitter with a Typed Event Map (node:events)

TypeScript from Zero, episode 39: TypeScript EventEmitter with a Typed Event Map (node:events). Full code and real outputs, step by step.

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Part 40

TypeScript keyof, typeof and Indexed Access Types (T[K]) Explained

TypeScript from Zero, episode 40: TypeScript keyof, typeof and Indexed Access Types (T[K]) Explained. Full code and real outputs, step by step.

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Part 41

TypeScript Mapped Types: [K in keyof T], readonly and Key Remapping with as

TypeScript from Zero, episode 41: TypeScript Mapped Types: [K in keyof T], readonly and Key Remapping with as. Full code and real outputs, step by step.

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Part 42

TypeScript Conditional Types and infer: T extends U ? X : Y

TypeScript from Zero, episode 42: TypeScript Conditional Types and infer: T extends U ? X : Y. Full code and real outputs, step by step.

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Part 43

TypeScript Template Literal Types: Typed Route Params from "/tasks/:id"

TypeScript from Zero, episode 43: TypeScript Template Literal Types: Typed Route Params from "/tasks/:id". Full code and real outputs, step by step.

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Part 44

TypeScript Function Overloads and this Types (Error TS2769 and TS2684)

TypeScript from Zero, episode 44: TypeScript Function Overloads and this Types (Error TS2769 and TS2684). Full code and real outputs, step by step.

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Part 45

TypeScript Declaration Files: .d.ts, declare module and @types Packages (TS7016)

TypeScript from Zero, episode 45: TypeScript Declaration Files: .d.ts, declare module and @types Packages (TS7016). Full code and real outputs, step by step.

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Part 46

TypeScript Branded Types (UserId vs TaskId) and readonly Arrays

TypeScript from Zero, episode 46: TypeScript Branded Types (UserId vs TaskId) and readonly Arrays. Full code and real outputs, step by step.

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Part 47

TypeScript Testing with Vitest: Unit Tests, Mocks (vi.fn) and expectTypeOf

TypeScript from Zero, episode 47: TypeScript Testing with Vitest: Unit Tests, Mocks (vi.fn) and expectTypeOf. Full code and real outputs, step by step.

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Part 48

TypeScript Linting: ESLint Flat Config, typescript-eslint and TS 7 (ERESOLVE Fix)

TypeScript from Zero, episode 48: TypeScript Linting: ESLint Flat Config, typescript-eslint and TS 7 (ERESOLVE Fix). Full code and real outputs, step by step.

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Part 49

TypeScript Project References: composite, tsc -b and Shared Types for CLI and API

TypeScript from Zero, episode 49: TypeScript Project References: composite, tsc -b and Shared Types for CLI and API. Full code and real outputs, step by step.

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Part 50

TypeScript: Publish a Typed npm Package (exports, types, files) + Series Recap

TypeScript from Zero, episode 50: TypeScript: Publish a Typed npm Package (exports, types, files) + Series Recap. Full code and real outputs, step by step.

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