Intro to Generics 9 exercises

TypeScript Generics

Section Resources
- Generics section of the TypeScript docs
  The TypeScript docs for generics have info and examples on creating and using generic types.
- The unknown Type from the TypeScript Docs
  Learn more about the unknown type in the TypeScript docs
- Generic Constraints from the TypeScript Docs
  The "Generic Constraints" page from the TypeScript documentation provides detailed information on how to define constraints for generic types
- 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.
- gesture.ts from the Excalidraw GitHub Repo
  See a real-world example of how generics are used in a software project.
- Total TypeScript - The Extends Keyword in action
  A refresher from the Type Transformations workshop lesson, "Support Function Type Constraints with Variable Arguments", showing extends in action.

Transcript

0:00 In this exercise, we have a function called returnWhatIPassIn. What we need to do is anything that we pass this function, we're just going to return it. Currently, this is typed as unknown. If you hover over this, then it's going to return unknown as well.

0:15 This isn't correct. We want it to return 1 if we pass in 1 and return matt if we pass in matt. These two types here are currently being inferred as unknown. Your job is to try to find a syntax that we can type this function with that will let us return whatever we want or rather, return what gets passed in.

0:37 You'll need to look in the generics section in terms of typing a function with a generic type. Good luck.

Problem

Typing Functions with Generics

In this exercise, we have a function called returnWhatIPassIn which takes a parameter t of type unknown:

const returnWhatIPassIn = (t: unknown) => {
  return t;
};

Currently, this is typed as unknown, so if you hover over this, it's going to return unknown as well.

Bec

Transcript

0:37 You'll need to look in the generics section in terms of typing a function with a generic type. Good luck.