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Type Force

A Learning TypeScript > Type Modifiers 🍲 entree project.

Greetings, hero. You have been carefully selected from a list of individuals who have demonstrated extraordinary powers in working with type systems. Welcome to the ✖ Type Force ✖.

Your powers in particular have manifested themselves in your ability to analyze situations for probable outcomes. How wondrously useful.

We need you to develop a prediction engine that harnesses your abilities for good. We've started what we can with a variable and a function, but sadly do not have type system expertise ourselves. Your task is to create a duel function that takes in descriptions of two fighters as tuples, and returns a tuple describing the victor. You'll also need to fill in type annotations in the existing code.

Setup​

If you haven't yet, set up the github.com/LearningTypeScript/projects repository locally.

shell
git clone https://github.com/LearningTypeScript/projects learning-typescript-projects
cd learning-typescript-projects
npm i
shell
git clone https://github.com/LearningTypeScript/projects learning-typescript-projects
cd learning-typescript-projects
npm i

Open your editor in this project's directory:

shell
code projects/type-modifiers/type-force
shell
code projects/type-modifiers/type-force

In one terminal, run the TypeScript compiler via the tsc script. For example, to start the TypeScript compiler in watch mode:

shell
npm run tsc -- --watch
shell
npm run tsc -- --watch

In another terminal, run Jest via the test script. For example, to start tests in watch mode:

shell
npm run test -- --watch
shell
npm run test -- --watch

Specification​

Create and export a duel function with two parameters, good and bad, both of which are objects containing the following properties:

  • mutations: Array of strings that are keys in the mutationsLibrary object
  • name: A string

Internally it will create a character for each variable. A character object can be created with the following steps:

  1. Initialize a flying property as false, and power and toughness as 1
  2. For each mutation in the power, run the corresponding function from mutationsLibrary on the character

The duel function's return type should be a read-only tuple containing two elements:

  1. Either "hero" or "villain", indicating who won, as computed by who has the higher of: their power divided by the other character's toughness
  2. The winning character object

Files​

  • index.ts: Add your types and duel function here
  • index.test.ts: Tests verifying your types and duel function
  • solution.ts: Solution code

Notes​

Note: your terminal should be in the type-force directory, not the root repository's directory.

  • The existing code has correct runtime behavior. You'll need to add type annotations to it, but don't delete any existing code.