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Commit 49c9ec8

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mattpocockmattpocock
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Added 14-16
1 parent 0e61654 commit 49c9ec8
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‎notes/FUTURE.md

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## Things to add
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- any vs unknown (use casting an error in a catch block as an example)
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- intersection types
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- classes
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- interface extends
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- Omit, Partial, Pick, Required, Record (object-based utility types)
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- ReadonlyArray
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- typeof narrowing
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- instanceof narrowing
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- limits of typeof narrowing (unknown and object)
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## Things NOT to add
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These things are out-of-scope, or will be included in other modules
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- limits of typeof narrowing (unknown and object)
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- Type predicates
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- Using external libraries and @types
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- discriminated unions

‎src/10-set.problem.ts

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@@ -19,5 +19,5 @@ it("Should give a type error when you try to pass a non-string", () => {
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it("Should be typed as an array of strings", () => {
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const guitaristsAsArray = Array.from(guitarists);
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type cases = [Expect<Equal<typeof guitaristsAsArray, string[]>>];
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type tests = [Expect<Equal<typeof guitaristsAsArray, string[]>>];
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});

‎src/10-set.solution.ts

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@@ -19,5 +19,5 @@ it("Should give a type error when you try to pass a non-string", () => {
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it("Should be typed as an array of strings", () => {
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const guitaristsAsArray = Array.from(guitarists);
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type cases = [Expect<Equal<typeof guitaristsAsArray, string[]>>];
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type tests = [Expect<Equal<typeof guitaristsAsArray, string[]>>];
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});

‎src/14-extends.problem.ts

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import { Equal, Expect } from "./helpers/type-utils";
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/**
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* Here, the id property is shared between all three
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* interfaces. Can you find a way to refactor this to
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* make it more DRY?
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*/
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interface User {
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id: string;
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firstName: string;
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lastName: string;
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}
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interface Post {
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id: string;
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title: string;
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body: string;
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}
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interface Comment {
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id: string;
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comment: string;
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}
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type tests = [
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Expect<Equal<User, { id: string; firstName: string; lastName: string }>>,
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Expect<Equal<Post, { id: string; title: string; body: string }>>,
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Expect<Equal<Comment, { id: string; comment: string }>>,
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];

‎src/14-extends.solution.ts

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import { Equal, Expect } from "./helpers/type-utils";
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/**
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* Here, the id property is shared between all three
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* interfaces. Can you find a way to refactor this to
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* make it more DRY?
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*/
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interface Base {
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id: string;
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}
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interface User extends Base {
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firstName: string;
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lastName: string;
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}
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interface Post extends Base {
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title: string;
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body: string;
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}
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interface Comment extends Base {
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comment: string;
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}
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type tests = [
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Expect<Equal<User, { id: string; firstName: string; lastName: string }>>,
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Expect<Equal<Post, { id: string; title: string; body: string }>>,
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Expect<Equal<Comment, { id: string; comment: string }>>,
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];

‎src/15-intersection.problem.ts

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interface User {
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id: string;
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firstName: string;
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lastName: string;
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}
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interface Post {
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id: string;
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title: string;
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body: string;
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}
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/**
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* How do we type this return statement so it's both
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* User AND { posts: Post[] }
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*/
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export const getDefaultUserAndPosts = (): unknown => {
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return {
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id: "1",
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firstName: "Matt",
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lastName: "Pocock",
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posts: [
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{
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id: "1",
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title: "How I eat so much cheese",
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body: "It's pretty edam difficult",
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},
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],
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};
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};
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const userAndPosts = getDefaultUserAndPosts();
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console.log(userAndPosts.posts[0]);

‎src/15-intersection.solution.ts

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interface User {
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id: string;
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firstName: string;
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lastName: string;
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}
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interface Post {
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id: string;
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title: string;
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body: string;
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}
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export const getDefaultUserAndPosts = (): User & { posts: Post[] } => {
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return {
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id: "1",
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firstName: "Matt",
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lastName: "Pocock",
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posts: [
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{
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id: "1",
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title: "How I eat so much cheese",
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body: "It's pretty edam difficult",
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},
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],
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};
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};
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const userAndPosts = getDefaultUserAndPosts();
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console.log(userAndPosts.posts[0]);

‎src/16-omit-and-pick.problem.ts

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import { Equal, Expect } from "./helpers/type-utils";
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interface User {
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id: string;
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firstName: string;
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lastName: string;
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}
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/**
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* How do we create a new object type with _only_ the
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* firstName and lastName properties of User?
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*/
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type MyType = unknown;
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type tests = [Expect<Equal<MyType, { firstName: string; lastName: string }>>];

‎src/16-omit-and-pick.solution.1.ts

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import { Equal, Expect } from "./helpers/type-utils";
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interface User {
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id: string;
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firstName: string;
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lastName: string;
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}
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/**
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* How do we create a new object type with _only_ the
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* firstName and lastName properties of User?
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*/
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type MyType = Omit<User, "id">;
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type tests = [Expect<Equal<MyType, { firstName: string; lastName: string }>>];

‎src/16-omit-and-pick.solution.2.ts

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import { Equal, Expect } from "./helpers/type-utils";
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interface User {
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id: string;
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firstName: string;
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lastName: string;
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}
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/**
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* How do we create a new object type with _only_ the
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* firstName and lastName properties of User?
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*/
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type MyType = Pick<User, "firstName" | "lastName">;
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type tests = [Expect<Equal<MyType, { firstName: string; lastName: string }>>];

‎src/98-extends.problem.ts

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