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07
TypeScript essentials

TypeScript essentials

The TypeScript you need on day one — without the type-gymnastics that scare people off.

~ 160 min·11 lessons·updated apr 2026

What you'll learn


Lessons

Read in order. Each lesson stands on its own, but the order is deliberate.

  1. 01
    Types vs values
    The two worlds, and why mixing them up is the #1 confusion.
    13 min
  2. 02
    Primitives and unions
    Building useful types out of the smallest pieces.
    14 min
  3. 03
    Objects and interfaces
    Records, optionality, readonly, index signatures.
    15 min
  4. 04
    Generics — gently
    Functions that keep their types. Start small.
    16 min
  5. 05
    Narrowing
    How TypeScript reads your code to refine types.
    16 min
  6. 06
    Discriminated unions
    The pattern that makes domain modeling pleasant.
    14 min
  7. 07
    Utility types
    Partial, Pick, Omit, Record — and the day you write your own.
    14 min
  8. 08
    Type vs interface
    Settling the argument with rules, not opinions.
    12 min
  9. 09
    Inference and contracts
    Where to annotate, where to let TS figure it out.
    14 min
  10. 10
    Common errors, decoded
    Reading the squiggle and what it's actually telling you.
    14 min
  11. 11
    Strict mode tips
    The flags worth turning on today.
    14 min

Prerequisites

  • · Comfortable with modern JavaScript
  • · Used a build tool before

After this, try