Added processed book saving to localstorage

src/utils/localStorage.ts

@@ -0,0 +1,14 @@
+import { IBook } from "../types/book";
+import { isArrOfStr } from "../types/utils";
+
+export const saveBook = (bookObj: IBook, key: string): void => {
+  const bookListStr = localStorage.getItem("list") || "[]";
+  const bookList: unknown = JSON.parse(bookListStr);
+
+  if (isArrOfStr(bookList) && !bookList.includes(key)) {
+    const newBookList = [key, ...bookList];
+
+    localStorage.setItem("list", JSON.stringify(newBookList));
+    localStorage.setItem(key, JSON.stringify(bookObj));
+  }
+};