Intro

About the Instructor

Frontend Masters instructor for 9 years
Developer Platform Lead @ Stripe
Designs Stripe’s API semantics
Architect responsible for TypeScript projects like node-stripe, Stripe Shell, and Stripe Workbench

Top Goals for this course

Pass along key knowledge gained through thousands of hours of TypeScript teaching, Q&A and pair programming
Give you a framework for understanding challenging type information.
Teach you how to understand and use a wide range of TypeScript’s built-in utility types

This likely is pretty scary right now, but you’ll know what it means by the end of the course

ts
// Get keys of type T whose values are assignable to type U
type FilteredKeys<T, U> = {
  [P in keyof T]: T[P] extends U ? P : never
}[keyof T] &
  keyof T
 
/**
 * get a subset of Document, consisting only of methods
 * returning an Element (e.g., querySelector) or an
 * Element[] (e.g., querySelectorAll)
 */
type ValueFilteredDoc = Pick<
  Document,
  FilteredKeys<
    Document,
    (...args: any[]) => Element | Element[]
  >
>Try

What do you assume I already know?

Modern javascript
The basics of function, object and array types
Basic generics (e.g., TypeScript Fundamentals v4 - Generics)
Index signatures

Also… some practical experience always helps!

Workshop Setup

As long as you can access the following websites, you should require no further setup

If you’d like to follow along with interactive examples, please install Volta

sh
curl https://get.volta.sh | bash # Linux / macOS only
volta install node@lts yarn@^3

Make sure to follow the installation instructions for volta — both what you see on the website and what you see in the CLI console. Next, clone the git repo for this course github.com/mike-north/typescript-courses, enter the directory, and run yarn to install all dependencies

sh
git clone https://github.com/mike-north/typescript-courses
cd typescript-courses
yarn

most of our work today will be in the packages/notes-intermediate-ts-v2 folder

sh
cd packages/notes-intermediate-ts-v2