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TypeScript for Application Developers

Go past annotations. Structural typing, narrowing, generics, and the type-level tools that make invalid states impossible.

·22,110 learners·12 lessons · 1h 55m·Updated Sep 2026

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TypeScript for Application Developers

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12 LESSONS

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YOUR INSTRUCTOR

Daniel Okafor

Daniel works on the layer where application code meets the database. He has spent years untangling type systems and query plans, usually in the same afternoon. He believes most runtime bugs are modelling mistakes that were visible earlier, and he teaches both TypeScript and Postgres from that angle.

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What you'll learn

Make invalid states unrepresentable

Model your domain so the compiler rejects the combinations that should never happen.

Write real generics

Build reusable functions and components that keep type information instead of erasing it.

Use the type-level toolkit

Apply conditional, mapped, and template literal types where they earn their complexity.

Type the boundaries

Validate and type the data crossing into your app, so external data stops being an any.

Course content

4 MODULES · 12 LESSONS · 1H 55M TOTAL

MODULE 01 How the Type System Thinks

The mental model underneath everything else: structural compatibility, unions, and narrowing.

3 LESSONS · 28M

1.1Structural typing and assignabilityFree preview11:49 1.2Unions and narrowing10:20 1.3Literal types and const assertions05:38

MODULE 02 Generics

Writing code that keeps type information flowing through it instead of collapsing to any.

3 LESSONS · 24M

2.1Generic functions and inference12:52 2.2Constraints and default type parameters04:13 2.3Generic components in React06:47

Every lesson, searchable to the second.

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