Add and search

Write book add and search functions.

The addBook function

The addBook function adds a new Book object to the library. You append it to the end of the array with push.

function addBook(lib: Library, book: Book): void {
  lib.books.push(book);
}

The searchByTitle function

searchByTitle finds books whose title contains a specific term. You use filter and check each book's title with includes.

function searchByTitle(lib: Library, title: string): Book[] {
  return lib.books.filter(b => b.title.includes(title));
}

Exercise Write add and search

Define Book, Member, Library interfaces. Write a function addBook(lib: Library, book: Book): void. Write a function searchByTitle(lib: Library, title: string): Book[]: search titles with filter and includes. Add two books ("TypeScript", "JavaScript") and search for "Script", print the number of matches.

Show example solution

interface Book { id: string; title: string; author: string; available: boolean; }
interface Member { id: string; name: string; }
interface Library { books: Book[]; }

function addBook(lib: Library, book: Book): void {
  lib.books.push(book);
}

function searchByTitle(lib: Library, title: string): Book[] {
  return lib.books.filter(b => b.title.includes(title));
}

const lib: Library = { books: [] };
addBook(lib, { id: "b1", title: "TypeScript", author: "Ada", available: true });
addBook(lib, { id: "b2", title: "JavaScript", author: "Bob", available: true });
const results = searchByTitle(lib, "Script");
console.log(results.length);

Test yourself

What does the searchByTitle function return?
- void
- A single Book
- number
- Book[] (matching books)
Show answer

Book[] (matching books) — searchByTitle returns all books whose title contains the search term as a new array. filter always returns a new array.

Complete the includes call

return lib.books.filter(b => b.title.____(title));

Show answer

return lib.books.filter(b => b.title.includes(title));

Add and search parts

addBook

Add a book to the library
searchByTitle

Search by title
lib.books.push(book)

Push a book to the list
b.title.includes(title)

Title check

Next lesson: Borrow

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