Passing Type Arguments 7 exercises

TypeScript Generics

Section Resources
- JavaScript Set from MDN
  MDN reference for the Set object in JavaScript, which is a collection of unique values.
- Classes section of the TypeScript docs
  The Classes section of the TypeScript docs provides detailed information on how to use generics with classes, including examples and best practices.
- Record Types from the TypesScript docs
  Documentation for the Record utility type in the TypeScript Handbook.
- TypeScript's reduce type signature from its source on GitHub
  TypeScript's reduce method signature on GitHub in the type declaration file used as a reference for JavaScript's built-in objects available in TypeScript.
- fetch, Response, and Body from TypeScript's DOM lib source on GitHub
  TypeScript's DOM lib provides the types for interacting with the Document Object Model.
- Awaited Utility Type from the TypeScript docs
  Documentation for the Awaited utility type in the TypeScript Handbook. This type can be used to extract the type of a Promise or Async value.
- Sengrid.ts from the Cal.com Github Repo
  A TypeScript class for interacting with the SendGrid email service in the cal.com repository.

Transcript

0:00 In this exercise, we have a function called createSet, and createSet just returns a Set. If you don't know what a Set is, it's just a part of JavaScript. It's like a unique set of values. We have a stringSet here, a numberSet and an unknownSet, and we're passing in a type argument here to createSet. OK, that's interesting.

0:22 This stringSet we can see here it's supposed to be Set<string> but actually it's Set<unknown>. This one is supposed to be Set, but it's Set. This one, we're happy with it, being Set. Your job is to figure out what this syntax is all about and how we can change this function to make this syntax behave as expected.

Problem

Add Type Parameters to a Function

In this exercise, we have a function called createSet which returns a Set which can only contain unique values:


export const createSet = () => { return new Set(); };

We also have a stringSet, a numberSet, and an unknownSet that each pass in a type argument to `createSe