feat: add checkDomain util function (#14)

Author: klmhyeonwoo

README.md

@@ -47,6 +47,7 @@ const difference = numberUtil.subtract(10, 3); // 7
 // Validation utilities
 const isValid = validationUtil.checkEmail("user@example.com"); // true
 const isHttpUrl = validationUtil.checkHttpUrl("https://example.com"); // true
+const isDomain = validationUtil.checkDomain("example.com"); // true
 
 // Common utilities
 const empty = commonUtil.isEmpty(""); // true
@@ -80,6 +81,7 @@ const theme = cookieUtil.getCookie("theme");
 
 - `checkEmail(email: string): boolean` - Validates email format
 - `checkHttpUrl(url: string): boolean` - Validates HTTP/HTTPS URL format
+- `checkDomain(domain: string): boolean` - Validates domain name format
 
 ### CommonUtil
 

package/validationUtil/checkDomain/index.test.ts

@@ -0,0 +1,16 @@
+import { describe, expect, test } from "vitest";
+import checkDomain from ".";
+
+describe("checkDomain 유틸 함수 테스트", () => {
+  test("유효한 도메인이 들어오는 경우 true를 반환한다.", () => {
+    expect(checkDomain("example.com")).toBe(true);
+    expect(checkDomain("sub.example.co.uk")).toBe(true);
+    expect(checkDomain("www.my-site123.org")).toBe(true);
+    expect(checkDomain("www.layerapp.io")).toBe(true);
+  });
+  test("유효하지 않은 도메인이 들어오는 경우 false를 반환한다.", () => {
+    expect(checkDomain("")).toBe(false);
+    expect(checkDomain("invalid_domain")).toBe(false);
+    expect(checkDomain("https://layerapp.io")).toBe(false);
+  });
+});

package/validationUtil/checkDomain/index.ts

@@ -0,0 +1,4 @@
+export default function checkDomain(domain: string): boolean {
+  const domainRegex = /^(?!:\/\/)([a-z0-9-]+\.)+[a-z]{2,}$/;
+  return domainRegex.test(domain);
+}

package/validationUtil/index.ts

@@ -1,2 +1,3 @@
 export { default as checkEmail } from "./checkEmail";
 export { default as checkHttpUrl } from "./checkHttpUrl";
+export { default as checkDomain } from "./checkDomain";