feat(utils): countOccurrencesInArray 유틸 함수 추가 (#159)

* feat(utils): countOccurrencesInArray 유틸 함수 추가

* docs: 문서 수정

.changeset/blue-jeans-film.md

@@ -0,0 +1,5 @@
+---
+'@modern-kit/utils': minor
+---
+
+feat(utils): countOccurrencesInArray 유틸 함수 추가 - @ssi02014

docs/docs/utils/array/countOccurrencesInArray.md

@@ -0,0 +1,34 @@
+# countOccurrencesInArray
+
+입력한 배열에서 배열의 각 요소들이 등장한 횟수를 카운팅 해주는 유틸 함수입니다.
+
+💡 단, `Object`, `Array`, `Set`, `Map`과 같은 객체 타입은 카운팅에서 제외되며, `null`, `NaN`, `undefined`는 카운팅에 포함됩니다.
+
+<br />
+
+## Code
+[🔗 실제 구현 코드 확인](https://github.com/modern-agile-team/modern-kit/blob/main/packages/utils/src/array/countOccurrencesInArray/index.ts)
+
+## Interface
+```ts title="typescript"
+const countOccurrencesInArray: <T extends readonly any[]>(
+  arr: T
+) => Record<Exclude<T[number], object>, number>;
+```
+
+## Usage
+```ts title="typescript"
+import { countOccurrencesInArray } from '@modern-kit/utils';
+
+const arr = [
+  'foo',
+  'foo',
+  'foo',
+  1,
+  1,
+  [1], // exclude
+  { a: 1 }, // exclude
+];
+
+const countingObj = countOccurrencesInArray(arr); // { foo: 3, 1: 2 }
+```

docs/docs/utils/validator/isArray.md

@@ -9,15 +9,14 @@
 
 ## Interface
 ```ts title="typescript"
-const isArray: <T>(value: unknown) => value is T[]
+const isArray: <T extends readonly any[]>(value: unknown) => value is T
 ```
 
 ## Usage
 ```ts title="typescript"
 import { isArray } from '@modern-kit/utils';
 
 isArray([]); // true
-
 isArray(() => {}); // false
 isArray('123'); // false
 isArray(123); // false

packages/utils/src/array/countOccurrencesInArray/countOccurrencesInArray.spec.ts

@@ -0,0 +1,66 @@
+import { countOccurrencesInArray } from '.';
+
+describe('countOccurrencesInArray', () => {
+  it('should count occurrences of each value correctly', () => {
+    const testArray1 = [
+      'foo',
+      'foo',
+      'foo',
+      1,
+      1,
+      false,
+      false,
+      null,
+      null,
+      undefined,
+      NaN,
+      [1], // exclude
+      { a: 1 }, // exclude
+      new Set(), // exclude
+      new Map(), // exclude
+    ];
+
+    expect(countOccurrencesInArray(testArray1)).toEqual({
+      foo: 3,
+      1: 2,
+      false: 2,
+      null: 2,
+      undefined: 1,
+      NaN: 1,
+    });
+
+    const testArray2: string[] = [];
+
+    expect(countOccurrencesInArray(testArray2)).toEqual({});
+  });
+
+  it('should correctly type the result object based on input array types', () => {
+    const readonlyTestArray = [
+      'foo',
+      'foo',
+      'bar',
+      1,
+      2,
+      [1], // exclude
+      { a: 1 }, // exclude
+    ] as const;
+
+    expectTypeOf(countOccurrencesInArray(readonlyTestArray)).toEqualTypeOf<
+      Record<'foo' | 1 | 2 | 'bar', number>
+    >();
+
+    const defaultTestArray = [
+      'foo',
+      'foo',
+      'bar',
+      1,
+      2,
+      [1], // exclude
+      { a: 1 }, // exclude
+    ];
+
+    expectTypeOf(countOccurrencesInArray(defaultTestArray)).toEqualTypeOf<
+      Record<string | number, number>
+    >();
+  });
+});

packages/utils/src/array/countOccurrencesInArray/index.ts

@@ -0,0 +1,13 @@
+export const countOccurrencesInArray = <T extends readonly any[]>(
+  arr: T
+): Record<Exclude<T[number], object>, number> => {
+  return arr.reduce((acc, cur) => {
+    if (typeof cur === 'object' && cur != null) {
+      return acc;
+    }
+
+    acc[cur] = (acc[cur] || 0) + 1;
+
+    return acc;
+  }, {});
+};

packages/utils/src/array/index.ts

@@ -0,0 +1 @@
+export * from './countOccurrencesInArray';

packages/utils/src/index.ts

@@ -1,3 +1,4 @@
+export * from './array';
 export * from './clipboard';
 export * from './common';
 export * from './device';

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

@@ -1,3 +1,5 @@
-export const isArray = <T>(value: unknown): value is Array<T> => {
+export const isArray = <T extends readonly any[]>(
+  value: unknown
+): value is T => {
   return Array.isArray(value);
 };

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

@@ -9,12 +9,18 @@ describe('isArray', () => {
   });
 
   it('should narrow the type through if statements', () => {
-    const testValue = ['foo'] as string | string[];
+    const defaultTestArray = ['foo'] as string | string[];
 
-    if (isArray<string>(testValue)) {
-      expectTypeOf(testValue).toEqualTypeOf<string[]>();
+    if (isArray(defaultTestArray)) {
+      expectTypeOf(defaultTestArray).toEqualTypeOf<string[]>();
     } else {
-      expectTypeOf(testValue).toEqualTypeOf<string>();
+      expectTypeOf(defaultTestArray).toEqualTypeOf<string>();
+    }
+
+    const readonlyTestArray = ['foo'] as const;
+
+    if (isArray(readonlyTestArray)) {
+      expectTypeOf(readonlyTestArray).toEqualTypeOf<readonly ['foo']>();
     }
   });
 });