add utility type and mapped type class code

Author: joshua1988

class-note/13_utility-type.ts

@@ -0,0 +1,72 @@
+interface Product {
+  id: number;
+  name: string;
+  price: number;
+  brand: string;
+  stock: number;
+}
+
+// 1. 상품 목록을 받아오기 위한 API 함수
+function fetchProducts(): Promise<Product[]> {
+  // ..
+}
+
+// interface ProductDetail {
+//   id: number; 
+//   name: string; 
+//   price: number;
+// }
+
+// 2. 특정 상품의 상세 정보를 나타내기 위한 함수
+type ShoppingItem = Pick<Product, 'id' | 'name' | 'price'>
+function displayProductDetail(shoppingItem: Pick<Product, 'id' | 'name' | 'price'>) {
+
+}
+
+// interface UpdateProduct {
+//   id?: number;
+//   name?: string;
+//   price?: number;
+//   brand?: string;
+//   stock?: number;
+// }
+
+type UpdateProduct = Partial<Product>
+// 3. 특정 상품 정보를 업데이트(갱신)하는 함수
+function updateProductItem(productItem: Partial<Product>) {
+
+}
+
+// 4. 유틸리티 타입 구현하기 - Partial
+interface UserProfile {
+  username: string;
+  email: string;
+  profilePhotoUrl: string;
+}
+// interface UserProfileUpdate {
+//   username?: string;
+//   email?: string;
+//   profilePhotoUrl?: string;
+// }
+// #1
+// type UserProfileUpdate = {
+//   username?: UserProfile['username'];
+//   email?: UserProfile['email'];
+//   profilePhotoUrl?: UserProfile['profilePhotoUrl'];
+// }
+
+// #2
+type UserProfileUpdate = {
+  [p in 'username' | 'email' | 'profilePhotoUrl']?: UserProfile[p]
+}
+type UserProfileKeys = keyof UserProfile
+
+// #3
+type UserProfileUpdate = {
+  [p in keyof UserProfile]?: UserProfile[p]
+}
+
+// #4
+type Subset<T> = {
+  [p in keyof T]?: T[p]
+}

class-note/14_mapped-type.ts

@@ -0,0 +1,13 @@
+type Heroes = 'Hulk' | 'Capt' | 'Thor'
+type HeroAges = { [K in Heroes]: number }
+const ages: HeroAges = {
+  Hulk: 33,
+  Capt: 100,
+  Thor: 1000,
+}
+
+// for in 반복문 코드
+// var arr = ['a','b','c'];
+// for (var key in arr) {
+//   console.log(arr[key]);
+// }