feat: add multiply util function

README.md

@@ -43,6 +43,7 @@ const frozen = objectUtil.deepFreeze({ a: { b: 1 } });
 // Number utilities
 const total = numberUtil.sum(1, 2, 3, 4, 5); // 15
 const difference = numberUtil.subtract(10, 3); // 7
+const product = numberUtil.multiply(2, 3, 4); // 24
 
 // Validation utilities
 const isValid = validationUtil.checkEmail("user@example.com"); // true
@@ -77,6 +78,7 @@ const theme = cookieUtil.getCookie("theme");
 
 - `sum(...numbers: number[]): number` - Calculates sum of numbers
 - `subtract(...numbers: number[]): number` - Calculates subtraction of numbers
+- `multiply(...numbers: number[]): number` - Calculates multiplication of numbers
 
 ### ValidationUtil
 

package/numberUtil/index.ts

@@ -1,2 +1,3 @@
 export { default as sum } from "./sum";
 export { default as subtract } from "./subtract";
+export { default as multiply } from "./multiply";

package/numberUtil/multiply/index.test.ts

@@ -0,0 +1,50 @@
+import { describe, test, expect } from "vitest";
+import multiply from ".";
+
+describe("multiply", () => {
+  describe("기본 케이스", () => {
+    test("두 양수를 올바르게 곱한다", () => {
+      expect(multiply(2, 3)).toBe(6);
+    });
+
+    test("여러 숫자를 올바르게 곱한다", () => {
+      expect(multiply(2, 3, 4)).toBe(24);
+    });
+
+    test("인수 중 0이 포함되면 0을 반환한다", () => {
+      expect(multiply(5, 10, 0, 20)).toBe(0);
+    });
+
+    test("음수를 올바르게 처리한다", () => {
+      expect(multiply(-5, 10)).toBe(-50);
+      expect(multiply(-5, -10)).toBe(50);
+    });
+
+    test("부동소수점을 올바르게 처리한다", () => {
+      expect(multiply(0.5, 10)).toBe(5);
+    });
+  });
+
+  describe("엣지 케이스", () => {
+    test("인수가 없을 때 1을 반환한다", () => {
+      expect(multiply()).toBe(1);
+    });
+
+    test("인수가 하나일 때 해당 숫자 자신을 반환한다", () => {
+      expect(multiply(7)).toBe(7);
+      expect(multiply(-100)).toBe(-100);
+    });
+
+    test("인수 중 NaN이 포함되면 NaN을 반환한다", () => {
+      expect(multiply(NaN)).toBeNaN();
+      expect(multiply(NaN, 7)).toBeNaN();
+      expect(multiply(5, NaN, 10)).toBeNaN();
+    });
+
+    test("Infinity(무한대)를 올바르게 처리한다", () => {
+      expect(multiply(Infinity, 2)).toBe(Infinity);
+      expect(multiply(Infinity, -2)).toBe(-Infinity);
+      expect(multiply(Infinity, 0)).toBeNaN();
+    });
+  });
+});

package/numberUtil/multiply/index.ts

@@ -0,0 +1,3 @@
+export default function multiply(...args: number[]): number {
+  return args.reduce((acc, curr) => acc * curr, 1);
+}