Add Redux and use it for state management

app/javascript/reducers/postReducer.ts

@@ -0,0 +1,34 @@
+import IPost from '../interfaces/IPost';
+
+const initialState: IPost = {
+  id: 0,
+  title: '',
+  description: null,
+  boardId: 0,
+  postStatusId: null,
+  userId: 0,
+  createdAt: '',
+};
+
+const postReducer = (
+  state = initialState,
+  action,
+): IPost => {
+  switch (action.type) {
+    case 'CONVERT':
+      return {
+        id: action.post.id,
+        title: action.post.title,
+        description: action.post.description,
+        boardId: action.post.board_id,
+        postStatusId: action.post.post_status_id,
+        userId: action.post.user_id,
+        createdAt: action.post.created_at,
+      };
+
+    default:
+      return state;
+  }
+}
+
+export default postReducer;