feat(@toss/utils): flatten array

packages/common/utils/src/array/flattenArray.en.md

@@ -0,0 +1,23 @@
+# flattenArray
+
+이차원 배열을 일차원 배열로 반환합니다.
+
+## Example
+
+```typescript
+// [1, 2, 3, 4]
+flattenArray([
+  [1, 2],
+  [3, 4],
+]);
+
+// [{ a: 1 }, { b: 2 }, { c: 3 }, { d: 4 }]
+flattenArray([
+  [{ a: 1 }, { b: 2 }],
+  [{ c: 3 }, { d: 4 }],
+]);
+
+// 일차원 배열을 입력했을 경우 입력받은 배열을 다시 그대로 반환합니다.
+// 1, 2, 3, 4
+flattenArray([1, 2, 3, 4]);
+```

packages/common/utils/src/array/flattenArray.ko.md

@@ -0,0 +1,23 @@
+# flattenArray
+
+이차원 배열을 일차원 배열로 반환합니다.
+
+## Example
+
+```typescript
+// [1, 2, 3, 4]
+flattenArray([
+  [1, 2],
+  [3, 4],
+]);
+
+// [{ a: 1 }, { b: 2 }, { c: 3 }, { d: 4 }]
+flattenArray([
+  [{ a: 1 }, { b: 2 }],
+  [{ c: 3 }, { d: 4 }],
+]);
+
+// 일차원 배열을 입력했을 경우 입력받은 배열을 다시 그대로 반환합니다.
+// 1, 2, 3, 4
+flattenArray([1, 2, 3, 4]);
+```

packages/common/utils/src/array/flattenArray.spec.ts

@@ -0,0 +1,28 @@
+import { flattenArray } from '.';
+
+describe('flattenArray', () => {
+  it('should work such that if a two-dimensional array is input, it returns a one-dimensional array', () => {
+    const twoDimensionsArray1 = [
+      [1, 2],
+      [3, 4],
+    ];
+    expect(flattenArray(twoDimensionsArray1)).toEqual([1, 2, 3, 4]);
+
+    const twoDimensionsArray2 = [
+      [{ a: 1 }, { b: 2 }],
+      [{ c: 3 }, { d: 4 }],
+    ];
+    expect(flattenArray(twoDimensionsArray2)).toEqual([{ a: 1 }, { b: 2 }, { c: 3 }, { d: 4 }]);
+
+    const twoDimensionsArray3 = [
+      ['', false, 0, undefined, null],
+      [null, undefined, 0, false, ''],
+    ];
+    expect(flattenArray(twoDimensionsArray3)).toEqual(['', false, 0, undefined, null, null, undefined, 0, false, '']);
+  });
+
+  it('should work by returning the array as is if a one-dimensional array is input', () => {
+    const oneDimensionsArray = [1, 2, 3, 4];
+    expect(flattenArray(oneDimensionsArray)).toEqual([1, 2, 3, 4]);
+  });
+});

packages/common/utils/src/array/flattenArray.ts

@@ -0,0 +1,13 @@
+/** @tossdocs-ignore */
+export function flattenArray<Type>(array: Type[]): Type[];
+export function flattenArray<Type>(array: Type[][]): Type[] {
+  if (array.length === 0) {
+    return array as Type[] & Type[][];
+  }
+
+  if (Array.isArray(array[0])) {
+    return (array as Type[][]).reduce((acc: Type[], curr: Type[]) => acc.concat(curr), []);
+  }
+
+  return array as Type[] & Type[][];
+}

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

@@ -1,8 +1,8 @@
 /** @tossdocs-ignore */
 export * from './arrayIncludes';
+export * from './flattenArray';
 export * from './isDifferentArray';
 export * from './isNonEmptyArray';
 export * from './last';
 export * from './NonEmptyArray';
 export * from './sample';
-