ts adv

ts_playground/06-union-type.ts

@@ -0,0 +1,11 @@
+type Input = string | number;
+
+function double(input: Input): number {
+    if (typeof input === "string")
+        return parseFloat(input) * 2;
+
+    return input * 2;
+}
+
+console.log(double(21));
+console.log(double("31"));

ts_playground/07-utility-types.ts

@@ -0,0 +1,25 @@
+type User2 = {
+    id: number;
+    name: string;
+    email: string;
+    password: string;
+};
+
+// 수정용 DTO에서 Partial로 일부만 허용
+type UpdateUserDto = Partial<User2>;
+
+// 공개용 DTO에서 비밀번호 제거
+type PublicUser = Omit<User2, 'password'>;
+
+const updateUser: UpdateUserDto = {
+    name: "update user",
+};
+
+const publicUser: PublicUser = {
+    id: 135,
+    name: "public user",
+    email: "pu@dor.com"
+};
+
+console.log(updateUser);
+console.log(publicUser);

ts_playground/08-record.ts

@@ -0,0 +1,10 @@
+type statusCode = "OK" | "ERROR" | "NOT_FOUND";
+
+// 매핑
+const statMessage: Record<statusCode, string> = {
+    OK: "정상 처리",
+    ERROR: "에러 발생",
+    NOT_FOUND: "찾을 수 없음"
+};
+
+console.log(statMessage.NOT_FOUND);

ts_playground/09-narrowing.ts

@@ -0,0 +1,10 @@
+function print(value: string | string[]) {
+    if (Array.isArray(value)) {
+        console.log("Array: ", value.join(", "));
+    } else {
+        console.log("Single value: ", value);
+    }
+}
+
+print("hello");
+print(["hello", "world"]);

ts_playground/10-keyof-typeof.ts

@@ -0,0 +1,21 @@
+type User3 = {
+    id: number;
+    name: string;
+};
+
+type User3Keys = keyof User3;
+
+function getValue(user: User3, key: User3Keys) {
+    return user[key];
+}
+
+const user3 = { id: 10, name: "dor" };
+console.log(getValue(user3, "name"));
+
+const config = {
+    port: 3000,
+    debug: true
+};
+
+type Config = typeof config;
+console.log(typeof config);

ts_playground/11-as-const.ts

@@ -0,0 +1,8 @@
+const ROLES = ["admin", "user", "guest"] as const;
+type Role = typeof ROLES[number];
+
+function checkRole(role: Role) {
+    console.log(`${role} 권한 확인`);
+}
+
+checkRole("admin");

ts_playground/12-unknown-never.ts

@@ -0,0 +1,18 @@
+function safeParse(json: string): unknown {
+    try {
+        return JSON.parse(json);
+    } catch {
+        return null;
+    }
+}
+
+const result = safeParse('{"name":"Dorr"}');
+console.log(result);
+
+if (typeof result === "object" && result !== null && "name" in result) {
+    console.log((result as { name: string }).name);
+}
+
+function fail(): never {
+    throw new Error("Failed!");
+}

ts_playground/tsconfig.json

@@ -12,7 +12,7 @@
 
     /* Language and Environment */
     "target": "es2023",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
-    // "lib": [],                                        /* Specify a set of bundled library declaration files that describe the target runtime environment. */
+    "lib": ["ES2020"],                                        /* Specify a set of bundled library declaration files that describe the target runtime environment. */
     // "jsx": "preserve",                                /* Specify what JSX code is generated. */
     // "libReplacement": true,                           /* Enable lib replacement. */
     // "experimentalDecorators": true,                   /* Enable experimental support for legacy experimental decorators. */