feat(utils): isPromise 함수 추가 (#90)

.changeset/honest-ads-sort.md

@@ -0,0 +1,5 @@
+---
+'@modern-kit/utils': patch
+---
+
+feat: isPromise 함수 및 테스트 코드 추가

docs/docs/utils/validator/isPromise.md

@@ -0,0 +1,23 @@
+# isPromise
+
+주어진 인자가 `Promise`인지 검사하는 함수입니다. Promise가 맞다면 타입을 좁혀줍니다.
+
+<br />
+
+## Interface
+```tsx title="typescript"
+const isPromise: <T = any>(value: any) => value is Promise<T>
+```
+
+## Usage
+```ts
+import { isPromise } from '@modern-kit/utils';
+
+isPromise(Promise.resolve()); // true
+
+isPromise(() => {}); // false
+isPromise('123'); // false
+isPromise(true); // false
+isPromise({}); // false
+isPromise(null); // false
+```

packages/utils/src/validator/index.ts

@@ -3,5 +3,6 @@ export * from './isFunction';
 export * from './isNotNullish';
 export * from './isNullish';
 export * from './isNumber';
+export * from './isPromise';
 export * from './isValidEmail';
 export * from './isValidPhoneNumberFormat';

packages/utils/src/validator/isPromise/index.ts

@@ -0,0 +1,3 @@
+export const isPromise = <T = any>(value: any): value is Promise<T> => {
+  return value instanceof Promise;
+};

packages/utils/src/validator/isPromise/isPromise.spec.ts

@@ -0,0 +1,23 @@
+import { isPromise } from '.';
+
+describe('isPromise', () => {
+  it('should return true if the given value is a Promise', () => {
+    expect(isPromise(Promise.resolve())).toBeTruthy();
+
+    expect(isPromise(() => {})).toBeFalsy();
+    expect(isPromise('123')).toBeFalsy();
+    expect(isPromise(true)).toBeFalsy();
+    expect(isPromise({})).toBeFalsy();
+    expect(isPromise(null)).toBeFalsy();
+  });
+
+  it('should narrow the type to Promise if isPromise returns true', () => {
+    const promise: any = Promise.resolve(1);
+
+    if (isPromise<number>(promise)) {
+      expectTypeOf(promise).toEqualTypeOf<Promise<number>>();
+    } else {
+      expectTypeOf(promise).toEqualTypeOf<any>();
+    }
+  });
+});