submmision for the task

src/challenge.ts

@@ -39,6 +39,13 @@ function addReview(
   comment: string
 ): ReviewedBook {
   // write your code here...
+  const newReview = {
+    reviewer: reviewer,
+    comment: comment,
+  };
+  if (newReview !== null) {
+    book.reviews?.push(newReview);
+  }
 
   return book;
 }

src/objects.ts

@@ -27,8 +27,14 @@ function createBook(
   genre: string
 ): Book {
   // write your code here...
+  const newBook: Book = {
+    title: title,
+    author: author,
+    publishedYear: publishedYear,
+    genre: genre,
+  };
 
-  return {} as Book; // replace "{} as Book" with what you see is fit
+  return { title, author, publishedYear, genre } as Book; // replace "{} as Book" with what you see is fit
 }
 
 // DO NOT CHANGE THE LINE OF CODE BELOW (you can use it for testing your code)
@@ -51,7 +57,7 @@ const book = createBook(
 function printBookTitleAndYear(book: Book): string {
   // write your code here...
 
-  return ""; // replace empty string with what you see is fit
+  return book.title + " " + book["publishedYear"]; // replace empty string with what you see is fit
 }
 
 /**
@@ -66,6 +72,7 @@ function printBookTitleAndYear(book: Book): string {
  */
 function addPageCount(book: Book, pageCount: number): Book {
   // write your code here...
+  book.pageCount = pageCount;
 
   return book;
 }
@@ -88,6 +95,7 @@ function addPageCount(book: Book, pageCount: number): Book {
  */
 function addISBN(book: Book, ISBN: string): Book {
   // write your code here...
+  book.ISBN = ISBN;
 
   return book;
 }
@@ -110,7 +118,7 @@ function addISBN(book: Book, ISBN: string): Book {
  */
 function updatePublishedYear(book: Book, newYear: number): Book {
   // write your code here...
-
+  book.publishedYear = newYear;
   return book;
 }
 
@@ -136,6 +144,14 @@ function updatePublishedYear(book: Book, newYear: number): Book {
 function addSecondAuthor(book: Book, additionalAuthor: string): Book {
   // write your code here...
 
+  if (Array.isArray(book.author)) {
+    // clause gaurd
+    book.author.push(additionalAuthor);
+  } else {
+    const author = book.author;
+    book.author = [author, additionalAuthor];
+  }
+
   return book;
 }