solved up to q18

Author: kylenoad

src/10-set.problem.ts

@@ -1,7 +1,7 @@
 import { expect, it } from "vitest";
 import { Equal, Expect } from "./helpers/type-utils";
 
-const guitarists = new Set();
+const guitarists = new Set<string>();
 
 guitarists.add("Jimi Hendrix");
 guitarists.add("Eric Clapton");

src/11-record.problem.ts

@@ -1,7 +1,7 @@
 import { expect, it } from "vitest";
 
 const createCache = () => {
-  const cache = {};
+  const cache: Record<string, string> = {};
 
   const add = (id: string, value: string) => {
     cache[id] = value;

src/12-typeof-narrowing.problem.ts

@@ -1,6 +1,12 @@
 import { expect, it } from "vitest";
 
-const coerceAmount = (amount: number | { amount: number }) => {};
+const coerceAmount = (amount: number | { amount: number }) => {
+  if(typeof amount === "number"){
+    return amount
+  }else{
+    return amount.amount
+  }
+};
 
 it("Should return the amount when passed an object", () => {
   expect(coerceAmount({ amount: 20 })).toEqual(20);

src/13-catch-blocks.problem.ts

@@ -5,7 +5,7 @@ const tryCatchDemo = (state: "fail" | "succeed") => {
     if (state === "fail") {
       throw new Error("Failure!");
     }
-  } catch (e) {
+  } catch (e: any) {
     return e.message;
   }
 };

src/14-extends.problem.ts

@@ -6,20 +6,21 @@ import { Equal, Expect } from "./helpers/type-utils";
  * make it more DRY?
  */
 
-interface User {
-  id: string;
+interface Base {
+  id: string
+}
+
+interface User extends Base{
   firstName: string;
   lastName: string;
 }
 
-interface Post {
-  id: string;
+interface Post extends Base{
   title: string;
   body: string;
 }
 
-interface Comment {
-  id: string;
+interface Comment extends Base {
   comment: string;
 }
 

src/15-intersection.problem.ts

@@ -14,7 +14,7 @@ interface Post {
  * How do we type this return statement so it's both
  * User AND { posts: Post[] }
  */
-export const getDefaultUserAndPosts = (): unknown => {
+export const getDefaultUserAndPosts = (): User & { posts: Post[] } => {
   return {
     id: "1",
     firstName: "Matt",

src/16-omit-and-pick.problem.ts

@@ -11,6 +11,6 @@ interface User {
  * firstName and lastName properties of User?
  */
 
-type MyType = unknown;
+type MyType = Omit<User, "id">;
 
 type tests = [Expect<Equal<MyType, { firstName: string; lastName: string }>>];

src/17-function-types.problem.ts

@@ -3,7 +3,7 @@ import { Equal, Expect } from "./helpers/type-utils";
 /**
  * How do we type onFocusChange?
  */
-const addListener = (onFocusChange: unknown) => {
+const addListener = (onFocusChange: (isFocused: boolean) => void) => {
   window.addEventListener("focus", () => {
     onFocusChange(true);
   });