Free course

TypeScript Course

Learn TypeScript from the JavaScript you already know: inference, annotations, objects, unions, functions, generics, narrowing, and compiler configuration.

6 modules · 42 lessons · No signup

Prerequisites: JavaScript

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What you'll learn

Add useful types to a small JavaScript program, configure the compiler, and handle uncertain data without turning type checking off.

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Course contents

  1. Start using TypeScript

    Install the compiler, run a first program, and read type errors.

    1. ✓ What TypeScript adds to JavaScript
    2. ✓ Install TypeScript in a project
    3. ✓ Write and compile your first program
    4. ✓ Read a TypeScript error
    5. ✓ Types do not change runtime behavior

  2. Types and inference

    Primitives, arrays, tuples, annotations, and special types.

    1. ✓ Let TypeScript infer obvious types
    2. ✓ Add a type annotation when it helps
    3. ✓ Use the primitive types
    4. ✓ Type arrays
    5. ✓ Use a tuple for fixed positions
    6. ✓ TypeScript: any vs unknown vs never
    7. ✓ Handle null and undefined deliberately
    8. ✓ Check your understanding: types and inference

  3. Objects and unions

    Describe object shapes and compose types deliberately.

    1. ✓ Describe an object shape
    2. ✓ TypeScript interfaces vs types: which one to use
    3. ✓ Optional and readonly properties
    4. ✓ TypeScript type for a string or array of strings
    5. ✓ Restrict values with literal unions
    6. ✓ Combine requirements with intersections
    7. ✓ Check your understanding: objects and unions

  4. Functions and generics

    Type calls, callbacks, reusable functions, and constraints.

    1. ✓ Type function parameters
    2. ✓ Use inferred and explicit return types
    3. ✓ Type callbacks
    4. ✓ Object destructuring with types in TypeScript
    5. ✓ TypeScript generics explained simply
    6. ✓ Constrain a generic only when necessary
    7. ✓ Check your understanding: functions and generics

  5. Narrowing uncertain values

    Refine unions with checks, guards, and discriminants.

    1. ✓ Narrow with typeof
    2. ✓ Narrow with equality, null checks, and truthiness
    3. ✓ Narrow with in and instanceof
    4. ✓ Model states with a discriminated union
    5. ✓ Type predicates and assertions
    6. ✓ Type narrowing and type guards in TypeScript
    7. ✓ Check your understanding: narrowing

  6. The compiler and runtime

    Configure strict checking and understand where types stop.

    1. ✓ Create a tsconfig.json
    2. ✓ Enable strict checking
    3. ✓ Type-check without emitting files
    4. ✓ Understand type erasure
    5. ✓ Use declaration files
    6. ✓ Validate data at runtime
    7. ✓ Build a typed task list
    8. ✓ Check your understanding: compiler and runtime