Repository: total-typescript/beginners-typescript-tutorial
Branch: main
Commit: e430c2da7ab0
Files: 57
Total size: 29.3 KB

Directory structure:
gitextract_69awz6n2/

├── .github/
│   └── workflows/
│       ├── renovate-checks.yml
│       └── section-repos.yml
├── .gitignore
├── .vscode/
│   └── settings.json
├── README.md
├── package.json
├── renovate.json
├── src/
│   ├── 01-number.problem.ts
│   ├── 01-number.solution.ts
│   ├── 02-object-param.problem.ts
│   ├── 02-object-param.solution.1.ts
│   ├── 02-object-param.solution.2.ts
│   ├── 02-object-param.solution.3.ts
│   ├── 03-optional-properties.problem.ts
│   ├── 03-optional-properties.solution.ts
│   ├── 04-optional-params.problem.ts
│   ├── 04-optional-params.solution.ts
│   ├── 05-assigning-types-to-variables.problem.ts
│   ├── 05-assigning-types-to-variables.solution.ts
│   ├── 06-unions.problem.ts
│   ├── 06-unions.solution.ts
│   ├── 07-arrays.problem.ts
│   ├── 07-arrays.solution.1.ts
│   ├── 07-arrays.solution.2.ts
│   ├── 08-function-return-type-annotations.problem.ts
│   ├── 08-function-return-type-annotations.solution.ts
│   ├── 09-promises.problem.ts
│   ├── 09-promises.solution.1.ts
│   ├── 09-promises.solution.2.ts
│   ├── 09-promises.solution.3.ts
│   ├── 10-set.problem.ts
│   ├── 10-set.solution.ts
│   ├── 11-record.problem.ts
│   ├── 11-record.solution.1.ts
│   ├── 11-record.solution.2.ts
│   ├── 11-record.solution.3.ts
│   ├── 12-typeof-narrowing.problem.ts
│   ├── 12-typeof-narrowing.solution.ts
│   ├── 13-catch-blocks.problem.ts
│   ├── 13-catch-blocks.solution.1.ts
│   ├── 13-catch-blocks.solution.2.ts
│   ├── 13-catch-blocks.solution.3.ts
│   ├── 14-extends.problem.ts
│   ├── 14-extends.solution.ts
│   ├── 15-intersection.problem.ts
│   ├── 15-intersection.solution.ts
│   ├── 16-omit-and-pick.problem.ts
│   ├── 16-omit-and-pick.solution.1.ts
│   ├── 16-omit-and-pick.solution.2.ts
│   ├── 17-function-types.problem.ts
│   ├── 17-function-types.solution.1.ts
│   ├── 17-function-types.solution.2.ts
│   ├── 18-function-types-with-promises.problem.ts
│   ├── 18-function-types-with-promises.solution.ts
│   └── helpers/
│       └── type-utils.ts
├── tsconfig.json
└── vite.config.mts

================================================
FILE CONTENTS
================================================

================================================
FILE: .github/workflows/renovate-checks.yml
================================================
name: Renovate Checks
on:
  push:
    branches:
      - "renovate/**"

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Main
        uses: actions/checkout@v4
        with:
          ref: main
          path: repo

      - name: Install Dependencies in Main
        run: (cd repo && npm install)
      - name: Create Snapshot In Main
        run: (cd repo && npx tt-cli take-snapshot ./snap.md)
      - name: Copy Snapshot To Outer Directory
        run: mv repo/snap.md ./snap.md
      - name: Delete Main Directory
        run: rm -rf repo
      - name: Checkout Branch
        uses: actions/checkout@v4
        with:
          path: repo
      - name: Install Dependencies in Branch
        run: (cd repo && npm install)
      - name: Move Snapshot To Branch
        run: mv ./snap.md repo/snap.md
      - name: Compare Snapshot In Branch
        run: (cd repo && npx tt-cli compare-snapshot ./snap.md)


================================================
FILE: .github/workflows/section-repos.yml
================================================
name: Create Section Repos
on:
  push:
    branches:
      - "main"

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

jobs:
  run:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20.x
      - run: git config --global user.email "total-typescript@bot.com"
      - run: git config --global user.name "Total TypeScript Bot"
      - run: npx @total-typescript/exercise-cli@latest create-section-repos
    env:
      GITHUB_TOKEN: ${{ secrets.MY_GITHUB_TOKEN }}
      GH_TOKEN: ${{ secrets.MY_GITHUB_TOKEN }}


================================================
FILE: .gitignore
================================================
node_modules
tsconfig.temp.json
dist
*.tsbuildinfo
*.prompt.*
.vscode/*.code-snippets

================================================
FILE: .vscode/settings.json
================================================
{
  "typescript.tsdk": "node_modules/typescript/lib",
  "typescript.enablePromptUseWorkspaceTsdk": true,
  "github.copilot.enable": {
    "*": false,
  },
  "explorer.sortOrder": "mixed",
}

================================================
FILE: README.md
================================================
<a href="https://totaltypescript.com/tutorials/beginners-typescript"><img src="https://res.cloudinary.com/total-typescript/image/upload/v1709297838/github--beginngers-typescript_2x_p7vtmw.jpg" alt="beginner typescript tutorial" /></a>

## Quickstart

Take the course on [Total TypeScript](https://totaltypescript.com/tutorials/beginners-typescript). There, you'll find:

- Video explanations for each problem and solution
- Transcripts
- Text explanations
- A built-in Stackblitz editor

```sh
# Installs all dependencies
npm install

# Asks you which exercise you'd like to run, and runs it
npm run exercise
```

## How to take the course

You'll notice that the course is split into exercises. Each exercise is split into a `*.problem` and a `*.solution`.

To take an exercise:

1. Run `npm run exercise`
2. Choose which exercise you'd like to run.

This course encourages **active, exploratory learning**. In the video, I'll explain a problem, and **you'll be asked to try to find a solution**. To attempt a solution, you'll need to:

1. Check out [TypeScript's docs](https://www.typescriptlang.org/docs/handbook/intro.html).
1. Try to find something that looks relevant.
1. Give it a go to see if it solves the problem.

You'll know if you've succeeded because the tests will pass.

**If you succeed**, or **if you get stuck**, unpause the video and check out the `*.solution`. You can see if your solution is better or worse than mine!

## Acknowledgements

Say thanks to Matt on [Twitter](https://twitter.com/mattpocockuk) or by joining his [Discord](https://discord.gg/8S5ujhfTB3). Consider signing up to his [Total TypeScript course](https://totaltypescript.com).

## Reference

### `npm run exercise`

Alias: `npm run e`

Open a prompt for choosing which exercise you'd like to run.


================================================
FILE: package.json
================================================
{
  "name": "beginners-typescript",
  "version": "1.0.0",
  "type": "module",
  "main": "index.js",
  "author": "Matt Pocock <mattpocockvoice@gmail.com>",
  "license": "GPL-3.0",
  "devDependencies": {
    "@total-typescript/exercise-cli": "^0.11.0",
    "@total-typescript/tsconfig": "^1.0.3",
    "@types/node": "^18.6.5",
    "cross-fetch": "^3.1.5",
    "jsdom": "^25.0.0",
    "typescript": "^5.4.5",
    "vite-tsconfig-paths": "^5.0.0",
    "vitest": "^2.0.0"
  },
  "scripts": {
    "exercise": "tt-cli run",
    "e": "npm run exercise",
    "solution": "tt-cli run --solution",
    "s": "npm run solution",
    "prepare": "tt-cli prepare-stackblitz",
    "e-01": "tt-cli run 01",
    "s-01": "tt-cli run 01 --solution",
    "e-02": "tt-cli run 02",
    "s-02": "tt-cli run 02 --solution",
    "e-03": "tt-cli run 03",
    "s-03": "tt-cli run 03 --solution",
    "e-04": "tt-cli run 04",
    "s-04": "tt-cli run 04 --solution",
    "e-05": "tt-cli run 05",
    "s-05": "tt-cli run 05 --solution",
    "e-06": "tt-cli run 06",
    "s-06": "tt-cli run 06 --solution",
    "e-07": "tt-cli run 07",
    "s-07": "tt-cli run 07 --solution",
    "e-08": "tt-cli run 08",
    "s-08": "tt-cli run 08 --solution",
    "e-09": "tt-cli run 09",
    "s-09": "tt-cli run 09 --solution",
    "e-10": "tt-cli run 10",
    "s-10": "tt-cli run 10 --solution",
    "e-11": "tt-cli run 11",
    "s-11": "tt-cli run 11 --solution",
    "e-12": "tt-cli run 12",
    "s-12": "tt-cli run 12 --solution",
    "e-13": "tt-cli run 13",
    "s-13": "tt-cli run 13 --solution",
    "e-14": "tt-cli run 14",
    "s-14": "tt-cli run 14 --solution",
    "e-15": "tt-cli run 15",
    "s-15": "tt-cli run 15 --solution",
    "e-16": "tt-cli run 16",
    "s-16": "tt-cli run 16 --solution",
    "e-17": "tt-cli run 17",
    "s-17": "tt-cli run 17 --solution",
    "e-18": "tt-cli run 18",
    "s-18": "tt-cli run 18 --solution"
  },
  "dependencies": {
    "@types/express": "^4.17.13",
    "express": "^4.18.1",
    "zod": "^3.17.10"
  }
}


================================================
FILE: renovate.json
================================================
{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": ["config:base"],
  "packageRules": [
    {
      "packagePatterns": ["*"],
      "excludePackagePatterns": [
        "typescript",
        "vitest",
        "jsdom",
        "prettier",
        "vite-tsconfig-paths",
        "react",
        "@types/react",
        "@total-typescript/exercise-cli",
        "zod"
      ],
      "enabled": false
    }
  ]
}


================================================
FILE: src/01-number.problem.ts
================================================
import { expect, it } from "vitest";

export const addTwoNumbers = (a, b) => {
  return a + b;
};

it("Should add the two numbers together", () => {
  expect(addTwoNumbers(2, 4)).toEqual(6);
  expect(addTwoNumbers(10, 10)).toEqual(20);
});


================================================
FILE: src/01-number.solution.ts
================================================
import { expect, it } from "vitest";

export const addTwoNumbers = (a: number, b: number) => {
  return a + b;
};

it("Should add the two numbers together", () => {
  expect(addTwoNumbers(2, 4)).toEqual(6);
  expect(addTwoNumbers(10, 10)).toEqual(20);
});


================================================
FILE: src/02-object-param.problem.ts
================================================
import { expect, it } from "vitest";

export const addTwoNumbers = (params) => {
  return params.first + params.second;
};

it("Should add the two numbers together", () => {
  expect(
    addTwoNumbers({
      first: 2,
      second: 4,
    }),
  ).toEqual(6);

  expect(
    addTwoNumbers({
      first: 10,
      second: 20,
    }),
  ).toEqual(30);
});


================================================
FILE: src/02-object-param.solution.1.ts
================================================
import { expect, it } from "vitest";

export const addTwoNumbers = (params: { first: number; second: number }) => {
  return params.first + params.second;
};

it("Should add the two numbers together", () => {
  expect(
    addTwoNumbers({
      first: 2,
      second: 4,
    }),
  ).toEqual(6);

  expect(
    addTwoNumbers({
      first: 10,
      second: 20,
    }),
  ).toEqual(30);
});


================================================
FILE: src/02-object-param.solution.2.ts
================================================
import { expect, it } from "vitest";

type AddTwoNumbersArgs = {
  first: number;
  second: number;
};

export const addTwoNumbers = (params: AddTwoNumbersArgs) => {
  return params.first + params.second;
};

it("Should add the two numbers together", () => {
  expect(
    addTwoNumbers({
      first: 2,
      second: 4,
    }),
  ).toEqual(6);

  expect(
    addTwoNumbers({
      first: 10,
      second: 20,
    }),
  ).toEqual(30);
});


================================================
FILE: src/02-object-param.solution.3.ts
================================================
import { expect, it } from "vitest";

interface AddTwoNumbersArgs {
  first: number;
  second: number;
}

export const addTwoNumbers = (params: AddTwoNumbersArgs) => {
  return params.first + params.second;
};

it("Should add the two numbers together", () => {
  expect(
    addTwoNumbers({
      first: 2,
      second: 4,
    }),
  ).toEqual(6);

  expect(
    addTwoNumbers({
      first: 10,
      second: 20,
    }),
  ).toEqual(30);
});


================================================
FILE: src/03-optional-properties.problem.ts
================================================
import { expect, it } from "vitest";

export const getName = (params: { first: string; last: string }) => {
  if (params.last) {
    return `${params.first} ${params.last}`;
  }
  return params.first;
};

it("Should work with just the first name", () => {
  const name = getName({
    first: "Matt",
  });

  expect(name).toEqual("Matt");
});

it("Should work with the first and last name", () => {
  const name = getName({
    first: "Matt",
    last: "Pocock",
  });

  expect(name).toEqual("Matt Pocock");
});


================================================
FILE: src/03-optional-properties.solution.ts
================================================
import { expect, it } from "vitest";

export const getName = (params: { first: string; last?: string }) => {
  if (params.last) {
    return `${params.first} ${params.last}`;
  }
  return params.first;
};

it("Should work with just the first name", () => {
  const name = getName({
    first: "Matt",
  });

  expect(name).toEqual("Matt");
});

it("Should work with the first and last name", () => {
  const name = getName({
    first: "Matt",
    last: "Pocock",
  });

  expect(name).toEqual("Matt Pocock");
});


================================================
FILE: src/04-optional-params.problem.ts
================================================
import { expect, it } from "vitest";

export const getName = (first: string, last: string) => {
  if (last) {
    return `${first} ${last}`;
  }
  return first;
};

it("Should work with just the first name", () => {
  const name = getName("Matt");

  expect(name).toEqual("Matt");
});

it("Should work with the first and last name", () => {
  const name = getName("Matt", "Pocock");

  expect(name).toEqual("Matt Pocock");
});


================================================
FILE: src/04-optional-params.solution.ts
================================================
import { expect, it } from "vitest";

export const getName = (first: string, last?: string) => {
  if (last) {
    return `${first} ${last}`;
  }
  return first;
};

it("Should work with just the first name", () => {
  const name = getName("Matt");

  expect(name).toEqual("Matt");
});

it("Should work with the first and last name", () => {
  const name = getName("Matt", "Pocock");

  expect(name).toEqual("Matt Pocock");
});


================================================
FILE: src/05-assigning-types-to-variables.problem.ts
================================================
import { expect, it } from "vitest";

interface User {
  id: number;
  firstName: string;
  lastName: string;
  isAdmin: boolean;
}

/**
 * How do we ensure that defaultUser is of type User
 * at THIS LINE - not further down in the code?
 */
const defaultUser = {};

const getUserId = (user: User) => {
  return user.id;
};

it("Should get the user id", () => {
  expect(getUserId(defaultUser)).toEqual(1);
});


================================================
FILE: src/05-assigning-types-to-variables.solution.ts
================================================
import { expect, it } from "vitest";

interface User {
  id: number;
  firstName: string;
  lastName: string;
  isAdmin: boolean;
}

/**
 * How do we ensure that defaultUser is of type User
 * at THIS LINE - not further down in the code?
 */
const defaultUser: User = {
  id: 1,
  firstName: "Matt",
  lastName: "Pocock",
  isAdmin: true,
};

const getUserId = (user: User) => {
  return user.id;
};

it("Should get the user id", () => {
  expect(getUserId(defaultUser)).toEqual(1);
});


================================================
FILE: src/06-unions.problem.ts
================================================
interface User {
  id: number;
  firstName: string;
  lastName: string;
  /**
   * How do we ensure that role is only one of:
   * - 'admin'
   * - 'user'
   * - 'super-admin'
   */
  role: string;
}

export const defaultUser: User = {
  id: 1,
  firstName: "Matt",
  lastName: "Pocock",
  // @ts-expect-error
  role: "I_SHOULD_NOT_BE_ALLOWED",
};


================================================
FILE: src/06-unions.solution.ts
================================================
interface User {
  id: number;
  firstName: string;
  lastName: string;
  /**
   * How do we ensure that role is only one of:
   * - 'admin'
   * - 'user'
   * - 'super-admin'
   */
  role: "admin" | "user" | "super-admin";
}

export const defaultUser: User = {
  id: 1,
  firstName: "Matt",
  lastName: "Pocock",
  // @ts-expect-error
  role: "I_SHOULD_NOT_BE_ALLOWED",
};


================================================
FILE: src/07-arrays.problem.ts
================================================
interface User {
  id: number;
  firstName: string;
  lastName: string;
  role: "admin" | "user" | "super-admin";
  posts: Post;
}

interface Post {
  id: number;
  title: string;
}

export const defaultUser: User = {
  id: 1,
  firstName: "Matt",
  lastName: "Pocock",
  role: "admin",
  posts: [
    {
      id: 1,
      title: "How I eat so much cheese",
    },
    {
      id: 2,
      title: "Why I don't eat more vegetables",
    },
  ],
};


================================================
FILE: src/07-arrays.solution.1.ts
================================================
interface User {
  id: number;
  firstName: string;
  lastName: string;
  role: "admin" | "user" | "super-admin";
  posts: Post[];
}

interface Post {
  id: number;
  title: string;
}

export const defaultUser: User = {
  id: 1,
  firstName: "Matt",
  lastName: "Pocock",
  role: "admin",
  posts: [
    {
      id: 1,
      title: "How I eat so much cheese",
    },
    {
      id: 2,
      title: "Why I don't eat more vegetables",
    },
  ],
};


================================================
FILE: src/07-arrays.solution.2.ts
================================================
interface User {
  id: number;
  firstName: string;
  lastName: string;
  role: "admin" | "user" | "super-admin";
  posts: Array<Post>;
}

interface Post {
  id: number;
  title: string;
}

export const defaultUser: User = {
  id: 1,
  firstName: "Matt",
  lastName: "Pocock",
  role: "admin",
  posts: [
    {
      id: 1,
      title: "How I eat so much cheese",
    },
    {
      id: 2,
      title: "Why I don't eat more vegetables",
    },
  ],
};


================================================
FILE: src/08-function-return-type-annotations.problem.ts
================================================
import { expect, it } from "vitest";

interface User {
  id: number;
  firstName: string;
  lastName: string;
  role: "admin" | "user" | "super-admin";
  posts: Array<Post>;
}

interface Post {
  id: number;
  title: string;
}

/**
 * How do we ensure that makeUser ALWAYS
 * returns a user?
 */
const makeUser = () => {
  return {};
};

it("Should return a valid user", () => {
  const user = makeUser();

  expect(user.id).toBeTypeOf("number");
  expect(user.firstName).toBeTypeOf("string");
  expect(user.lastName).toBeTypeOf("string");
  expect(user.role).to.be.oneOf(["super-admin", "admin", "user"]);

  expect(user.posts[0].id).toBeTypeOf("number");
  expect(user.posts[0].title).toBeTypeOf("string");
});


================================================
FILE: src/08-function-return-type-annotations.solution.ts
================================================
import { expect, it } from "vitest";

interface User {
  id: number;
  firstName: string;
  lastName: string;
  role: "admin" | "user" | "super-admin";
  posts: Array<Post>;
}

interface Post {
  id: number;
  title: string;
}

/**
 * How do we ensure that makeUser ALWAYS
 * returns a user?
 */
const makeUser = (): User => {
  return {
    id: 1,
    firstName: "Matt",
    lastName: "Pocock",
    role: "admin",
    posts: [
      {
        id: 1,
        title: "How I eat so much cheese",
      },
    ],
  };
};

it("Should return a valid user", () => {
  const user = makeUser();

  expect(user.id).toBeTypeOf("number");
  expect(user.firstName).toBeTypeOf("string");
  expect(user.lastName).toBeTypeOf("string");
  expect(user.role).to.be.oneOf(["super-admin", "admin", "user"]);

  expect(user.posts[0].id).toBeTypeOf("number");
  expect(user.posts[0].title).toBeTypeOf("string");
});


================================================
FILE: src/09-promises.problem.ts
================================================
interface LukeSkywalker {
  name: string;
  height: string;
  mass: string;
  hair_color: string;
  skin_color: string;
  eye_color: string;
  birth_year: string;
  gender: string;
}

export const fetchLukeSkywalker = async (): LukeSkywalker => {
  const data = await fetch("https://swapi.py4e.com/api/people/1").then(
    (res) => {
      return res.json();
    }
  );

  return data;
};


================================================
FILE: src/09-promises.solution.1.ts
================================================
interface LukeSkywalker {
  name: string;
  height: string;
  mass: string;
  hair_color: string;
  skin_color: string;
  eye_color: string;
  birth_year: string;
  gender: string;
}

export const fetchLukeSkywalker = async (): Promise<LukeSkywalker> => {
  const data = await fetch("https://swapi.py4e.com/api/people/1").then(
    (res) => {
      return res.json();
    }
  );

  return data;
};


================================================
FILE: src/09-promises.solution.2.ts
================================================
interface LukeSkywalker {
  name: string;
  height: string;
  mass: string;
  hair_color: string;
  skin_color: string;
  eye_color: string;
  birth_year: string;
  gender: string;
}

export const fetchLukeSkywalker = async () => {
  const data = await fetch("https://swapi.py4e.com/api/people/1").then(
    (res) => {
      return res.json();
    }
  );

  return data as LukeSkywalker;
};


================================================
FILE: src/09-promises.solution.3.ts
================================================
interface LukeSkywalker {
  name: string;
  height: string;
  mass: string;
  hair_color: string;
  skin_color: string;
  eye_color: string;
  birth_year: string;
  gender: string;
}

export const fetchLukeSkywalker = async () => {
  const data: LukeSkywalker = await fetch(
    "https://swapi.py4e.com/api/people/1"
  ).then((res) => {
    return res.json();
  });

  return data;
};


================================================
FILE: src/10-set.problem.ts
================================================
import { expect, it } from "vitest";
import { Equal, Expect } from "./helpers/type-utils";

const guitarists = new Set();

guitarists.add("Jimi Hendrix");
guitarists.add("Eric Clapton");

it("Should contain Jimi and Eric", () => {
  expect(guitarists.has("Jimi Hendrix")).toEqual(true);
  expect(guitarists.has("Eric Clapton")).toEqual(true);
});

it("Should give a type error when you try to pass a non-string", () => {
  // @ts-expect-error
  guitarists.add(2);
});

it("Should be typed as an array of strings", () => {
  const guitaristsAsArray = Array.from(guitarists);

  type tests = [Expect<Equal<typeof guitaristsAsArray, string[]>>];
});


================================================
FILE: src/10-set.solution.ts
================================================
import { expect, it } from "vitest";
import { Equal, Expect } from "./helpers/type-utils";

const guitarists = new Set<string>();

guitarists.add("Jimi Hendrix");
guitarists.add("Eric Clapton");

it("Should contain Jimi and Eric", () => {
  expect(guitarists.has("Jimi Hendrix")).toEqual(true);
  expect(guitarists.has("Eric Clapton")).toEqual(true);
});

it("Should give a type error when you try to pass a non-string", () => {
  // @ts-expect-error
  guitarists.add(2);
});

it("Should be typed as an array of strings", () => {
  const guitaristsAsArray = Array.from(guitarists);

  type tests = [Expect<Equal<typeof guitaristsAsArray, string[]>>];
});


================================================
FILE: src/11-record.problem.ts
================================================
import { expect, it } from "vitest";

const createCache = () => {
  const cache = {};

  const add = (id: string, value: string) => {
    cache[id] = value;
  };

  const remove = (id: string) => {
    delete cache[id];
  };

  return {
    cache,
    add,
    remove,
  };
};

it("Should add values to the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");

  expect(cache.cache["123"]).toEqual("Matt");
});

it("Should remove values from the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");
  cache.remove("123");

  expect(cache.cache["123"]).toEqual(undefined);
});


================================================
FILE: src/11-record.solution.1.ts
================================================
import { expect, it } from "vitest";

const createCache = () => {
  const cache: Record<string, string> = {};

  const add = (id: string, value: string) => {
    cache[id] = value;
  };

  const remove = (id: string) => {
    delete cache[id];
  };

  return {
    cache,
    add,
    remove,
  };
};

it("Should add values to the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");

  expect(cache.cache["123"]).toEqual("Matt");
});

it("Should remove values from the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");
  cache.remove("123");

  expect(cache.cache["123"]).toEqual(undefined);
});


================================================
FILE: src/11-record.solution.2.ts
================================================
import { expect, it } from "vitest";

const createCache = () => {
  const cache: {
    [id: string]: string;
  } = {};

  const add = (id: string, value: string) => {
    cache[id] = value;
  };

  const remove = (id: string) => {
    delete cache[id];
  };

  return {
    cache,
    add,
    remove,
  };
};

it("Should add values to the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");

  expect(cache.cache["123"]).toEqual("Matt");
});

it("Should remove values from the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");
  cache.remove("123");

  expect(cache.cache["123"]).toEqual(undefined);
});


================================================
FILE: src/11-record.solution.3.ts
================================================
import { expect, it } from "vitest";

interface Cache {
  [id: string]: string;
}

const createCache = () => {
  const cache: Cache = {};

  const add = (id: string, value: string) => {
    cache[id] = value;
  };

  const remove = (id: string) => {
    delete cache[id];
  };

  return {
    cache,
    add,
    remove,
  };
};

it("Should add values to the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");

  expect(cache.cache["123"]).toEqual("Matt");
});

it("Should remove values from the cache", () => {
  const cache = createCache();

  cache.add("123", "Matt");
  cache.remove("123");

  expect(cache.cache["123"]).toEqual(undefined);
});


================================================
FILE: src/12-typeof-narrowing.problem.ts
================================================
import { expect, it } from "vitest";

const coerceAmount = (amount: number | { amount: number }) => {};

it("Should return the amount when passed an object", () => {
  expect(coerceAmount({ amount: 20 })).toEqual(20);
});

it("Should return the amount when passed a number", () => {
  expect(coerceAmount(20)).toEqual(20);
});


================================================
FILE: src/12-typeof-narrowing.solution.ts
================================================
import { expect, it } from "vitest";

const coerceAmount = (amount: number | { amount: number }) => {
  if (typeof amount === "number") {
    return amount;
  }
  return amount.amount;
};

it("Should return the amount when passed an object", () => {
  expect(coerceAmount({ amount: 20 })).toEqual(20);
});

it("Should return the amount when passed a number", () => {
  expect(coerceAmount(20)).toEqual(20);
});


================================================
FILE: src/13-catch-blocks.problem.ts
================================================
import { expect, it } from "vitest";

const tryCatchDemo = (state: "fail" | "succeed") => {
  try {
    if (state === "fail") {
      throw new Error("Failure!");
    }
  } catch (e) {
    return e.message;
  }
};

it("Should return the message when it fails", () => {
  expect(tryCatchDemo("fail")).toEqual("Failure!");
});


================================================
FILE: src/13-catch-blocks.solution.1.ts
================================================
import { expect, it } from "vitest";

const tryCatchDemo = (state: "fail" | "succeed") => {
  try {
    if (state === "fail") {
      throw new Error("Failure!");
    }
  } catch (e: any) {
    return e.message;
  }
};

it("Should return the message when it fails", () => {
  expect(tryCatchDemo("fail")).toEqual("Failure!");
});


================================================
FILE: src/13-catch-blocks.solution.2.ts
================================================
import { expect, it } from "vitest";

const tryCatchDemo = (state: "fail" | "succeed") => {
  try {
    if (state === "fail") {
      throw new Error("Failure!");
    }
  } catch (e) {
    return (e as Error).message;
  }
};

it("Should return the message when it fails", () => {
  expect(tryCatchDemo("fail")).toEqual("Failure!");
});


================================================
FILE: src/13-catch-blocks.solution.3.ts
================================================
import { expect, it } from "vitest";

const tryCatchDemo = (state: "fail" | "succeed") => {
  try {
    if (state === "fail") {
      throw new Error("Failure!");
    }
  } catch (e) {
    if (e instanceof Error) {
      return e.message;
    }
  }
};

it("Should return the message when it fails", () => {
  expect(tryCatchDemo("fail")).toEqual("Failure!");
});


================================================
FILE: src/14-extends.problem.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

/**
 * Here, the id property is shared between all three
 * interfaces. Can you find a way to refactor this to
 * make it more DRY?
 */

interface User {
  id: string;
  firstName: string;
  lastName: string;
}

interface Post {
  id: string;
  title: string;
  body: string;
}

interface Comment {
  id: string;
  comment: string;
}

type tests = [
  Expect<Equal<User, { id: string; firstName: string; lastName: string }>>,
  Expect<Equal<Post, { id: string; title: string; body: string }>>,
  Expect<Equal<Comment, { id: string; comment: string }>>,
];


================================================
FILE: src/14-extends.solution.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

/**
 * Here, the id property is shared between all three
 * interfaces. Can you find a way to refactor this to
 * make it more DRY?
 */

interface Base {
  id: string;
}

interface User extends Base {
  firstName: string;
  lastName: string;
}

interface Post extends Base {
  title: string;
  body: string;
}

interface Comment extends Base {
  comment: string;
}

type tests = [
  Expect<Equal<User, { id: string; firstName: string; lastName: string }>>,
  Expect<Equal<Post, { id: string; title: string; body: string }>>,
  Expect<Equal<Comment, { id: string; comment: string }>>,
];


================================================
FILE: src/15-intersection.problem.ts
================================================
interface User {
  id: string;
  firstName: string;
  lastName: string;
}

interface Post {
  id: string;
  title: string;
  body: string;
}

/**
 * How do we type this return statement so it's both
 * User AND { posts: Post[] }
 */
export const getDefaultUserAndPosts = (): unknown => {
  return {
    id: "1",
    firstName: "Matt",
    lastName: "Pocock",
    posts: [
      {
        id: "1",
        title: "How I eat so much cheese",
        body: "It's pretty edam difficult",
      },
    ],
  };
};

const userAndPosts = getDefaultUserAndPosts();

console.log(userAndPosts.posts[0]);


================================================
FILE: src/15-intersection.solution.ts
================================================
interface User {
  id: string;
  firstName: string;
  lastName: string;
}

interface Post {
  id: string;
  title: string;
  body: string;
}

export const getDefaultUserAndPosts = (): User & { posts: Post[] } => {
  return {
    id: "1",
    firstName: "Matt",
    lastName: "Pocock",
    posts: [
      {
        id: "1",
        title: "How I eat so much cheese",
        body: "It's pretty edam difficult",
      },
    ],
  };
};

const userAndPosts = getDefaultUserAndPosts();

console.log(userAndPosts.posts[0]);


================================================
FILE: src/16-omit-and-pick.problem.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

interface User {
  id: string;
  firstName: string;
  lastName: string;
}

/**
 * How do we create a new object type with _only_ the
 * firstName and lastName properties of User?
 */

type MyType = unknown;

type tests = [Expect<Equal<MyType, { firstName: string; lastName: string }>>];


================================================
FILE: src/16-omit-and-pick.solution.1.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

interface User {
  id: string;
  firstName: string;
  lastName: string;
}

/**
 * How do we create a new object type with _only_ the
 * firstName and lastName properties of User?
 */

type MyType = Omit<User, "id">;

type tests = [Expect<Equal<MyType, { firstName: string; lastName: string }>>];


================================================
FILE: src/16-omit-and-pick.solution.2.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

interface User {
  id: string;
  firstName: string;
  lastName: string;
}

/**
 * How do we create a new object type with _only_ the
 * firstName and lastName properties of User?
 */

type MyType = Pick<User, "firstName" | "lastName">;

type tests = [Expect<Equal<MyType, { firstName: string; lastName: string }>>];


================================================
FILE: src/17-function-types.problem.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

/**
 * How do we type onFocusChange?
 */
const addListener = (onFocusChange: unknown) => {
  window.addEventListener("focus", () => {
    onFocusChange(true);
  });

  window.addEventListener("blur", () => {
    onFocusChange(false);
  });
};

addListener((isFocused) => {
  console.log({ isFocused });

  type tests = [Expect<Equal<typeof isFocused, boolean>>];
});


================================================
FILE: src/17-function-types.solution.1.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

/**
 * How do we type onFocusChange?
 */
const addListener = (onFocusChange: (isFocused: boolean) => void) => {
  window.addEventListener("focus", () => {
    onFocusChange(true);
  });

  window.addEventListener("blur", () => {
    onFocusChange(false);
  });
};

addListener((isFocused) => {
  console.log({ isFocused });

  type tests = [Expect<Equal<typeof isFocused, boolean>>];
});


================================================
FILE: src/17-function-types.solution.2.ts
================================================
import { Equal, Expect } from "./helpers/type-utils";

/**
 * How do we type onFocusChange?
 */
type FocusListener = (isFocused: boolean) => void;

const addListener = (onFocusChange: FocusListener) => {
  window.addEventListener("focus", () => {
    onFocusChange(true);
  });

  window.addEventListener("blur", () => {
    onFocusChange(false);
  });
};

addListener((isFocused) => {
  console.log({ isFocused });

  type tests = [Expect<Equal<typeof isFocused, boolean>>];
});


================================================
FILE: src/18-function-types-with-promises.problem.ts
================================================
import { expect, it } from "vitest";

interface User {
  id: string;
  firstName: string;
  lastName: string;
}

const createThenGetUser = async (
  createUser: unknown,
  getUser: unknown,
): Promise<User> => {
  const userId: string = await createUser();

  const user = await getUser(userId);

  return user;
};

it("Should create the user, then get them", async () => {
  const user = await createThenGetUser(
    async () => "123",
    async (id) => ({
      id,
      firstName: "Matt",
      lastName: "Pocock",
    }),
  );

  expect(user).toEqual({
    id: "123",
    firstName: "Matt",
    lastName: "Pocock",
  });
});


================================================
FILE: src/18-function-types-with-promises.solution.ts
================================================
import { expect, it } from "vitest";

interface User {
  id: string;
  firstName: string;
  lastName: string;
}

const createThenGetUser = async (
  createUser: () => Promise<string>,
  getUser: (id: string) => Promise<User>,
): Promise<User> => {
  const userId: string = await createUser();

  const user = await getUser(userId);

  return user;
};

it("Should create the user, then get them", async () => {
  const user = await createThenGetUser(
    async () => "123",
    async (id) => ({
      id,
      firstName: "Matt",
      lastName: "Pocock",
    }),
  );

  expect(user).toEqual({
    id: "123",
    firstName: "Matt",
    lastName: "Pocock",
  });
});


================================================
FILE: src/helpers/type-utils.ts
================================================
export type Expect<T extends true> = T;
export type ExpectTrue<T extends true> = T;
export type ExpectFalse<T extends false> = T;
export type IsTrue<T extends true> = T;
export type IsFalse<T extends false> = T;

export type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends <
  T,
>() => T extends Y ? 1 : 2
  ? true
  : false;
export type NotEqual<X, Y> = true extends Equal<X, Y> ? false : true;

// https://stackoverflow.com/questions/49927523/disallow-call-with-any/49928360#49928360
export type IsAny<T> = 0 extends 1 & T ? true : false;
export type NotAny<T> = true extends IsAny<T> ? false : true;

export type Debug<T> = { [K in keyof T]: T[K] };
export type MergeInsertions<T> = T extends object
  ? { [K in keyof T]: MergeInsertions<T[K]> }
  : T;

export type Alike<X, Y> = Equal<MergeInsertions<X>, MergeInsertions<Y>>;

export type ExpectExtends<VALUE, EXPECTED> = EXPECTED extends VALUE
  ? true
  : false;
export type ExpectValidArgs<
  FUNC extends (...args: any[]) => any,
  ARGS extends any[],
> = ARGS extends Parameters<FUNC> ? true : false;

export type UnionToIntersection<U> = (
  U extends any ? (k: U) => void : never
) extends (k: infer I) => void
  ? I
  : never;


================================================
FILE: tsconfig.json
================================================
{
  "extends": "@total-typescript/tsconfig/bundler",
  "compilerOptions": {
    "noUncheckedIndexedAccess": false,
    "verbatimModuleSyntax": false
  },
  "include": [
    "src"
  ]
}

================================================
FILE: vite.config.mts
================================================
import { defineConfig } from "vitest/config";
import tsconfigPaths from "vite-tsconfig-paths";

export default defineConfig({
  test: {
    include: ["src/**/*{problem,solution,explainer}*.{ts,tsx}"],
    passWithNoTests: true,
    environment: "jsdom",
  },
  plugins: [tsconfigPaths()],
});