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Treasure Hunter

A Learning TypeScript > Generics 🍲 entree project.

Good evening, professor. We're with the National Typeological Survey. We've received word that there is a new system of catacombs and tunnels beneath your city. We'd like you to explore them.

Please submit a collectTreasure function to us that can recursively sift through buried contents. We will provide you functions to determine what is fake, real, or general scrap.


If you haven't yet, set up the repository locally.

git clone learning-typescript-projects
cd learning-typescript-projects
npm i

Change your terminal directory to this project's:

cd projects/generics/treasure-hunter

In a terminal, start the TypeScript compiler in watch mode:

tsc --watch

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

npm test -- --watch


Export a collectTreasure function. It should have three type parameters: Content, Fake, and Real. Fake and Real should both extend Content.

The collectTreasure function should have three runtime parameters:

  • buried: A Buried object (see later) of Content data
  • isFake: A type predicate function that takes in a datum and returns whether it is Fake
  • isReal: A type predicate function that takes in a datum and returns whether it is Real

Also create and export a Buried interface with a single type parameter. Each Buried object can be one of three things:

  • An array of the same type of Buried objects
  • A NextArea object, which can be either:
    • A Catacomb shape, with properties:
      • contents: A Buried object of the same type
      • type: "catacomb"
    • A TunnelSystem shape, with properties:
      • tunnels: An array of Buried objects of the same type
      • type: "tunnels"

The collectTreasure function should return an object with three properties:

  • fake: Array of found Fake items
  • real: Array of found Feal items
  • scrap: Array of all other items


  • Don't use any or leave any implicit anys.