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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));
}

Practice 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.

Starter code

index.ts
// Book, Member, Library arayüzlerini tanımla
// addBook(lib: Library, book: Book): void yaz
// searchByTitle(lib: Library, title: string): Book[] yaz
// iki kitap ekle, bir başlıkla ara ve eşleşen sayısını yazdır

Sample solution

index.ts
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);

Expected output

2

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What does the searchByTitle function return?

  • void
  • A single Book
  • number
  • Book[] (matching books) Correct answer

Explanation: searchByTitle returns all books whose title contains the search term as a new array. filter always returns a new array.

2 Complete the includes call

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

Explanation: The string includes method checks whether a substring is present. find is an array method; has and contains do not exist on strings.

3 Add and search parts

Term Meaning
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

All lessons in Beginner

1 TypeScript intro and setup

  1. What is TypeScript?
  2. Why TypeScript?
  3. tsc compiler
  4. tsconfig basics
  5. Summary - TypeScript basics

2 Primitive types

  1. string type
  2. number type
  3. boolean type
  4. let and const
  5. Summary - Primitive types

3 Arrays

  1. Array type
  2. Array methods
  3. readonly arrays
  4. Multidimensional arrays
  5. Summary - Arrays

4 Tuples

  1. What is a tuple?
  2. Tuple usage
  3. readonly tuple
  4. Summary - Tuple

5 Enums

  1. Numeric enum
  2. String enum
  3. const enum
  4. Enum members
  5. Summary - Enum

6 any, unknown, never

  1. any type
  2. unknown type
  3. never type
  4. void type
  5. Summary - Special types

7 Type annotation

  1. Variable annotation
  2. Parameter annotation
  3. Return type annotation
  4. Summary - Type annotation

8 Type inference

  1. Basic inference
  2. Inference with const
  3. Best common type
  4. Summary - Type inference

9 Objects

  1. Object type
  2. Optional properties
  3. Readonly properties
  4. Summary - Objects

10 Functions

  1. Function declaration
  2. Optional and default params
  3. Rest params
  4. Function overloads
  5. Summary - Functions

11 Arrow functions

  1. Arrow syntax
  2. this with arrow
  3. Arrow type
  4. Summary - Arrow functions

12 Interfaces

  1. What is an interface?
  2. Property types
  3. Interface vs type alias
  4. Summary - Interfaces

13 Type alias

  1. What is a type alias?
  2. Composition with alias
  3. Alias vs interface
  4. Summary - Type alias

14 Union and intersection

  1. Union types
  2. Intersection types
  3. Literal types
  4. Summary - Union & intersection

15 null and undefined

  1. null vs undefined
  2. Optional chaining
  3. Nullish coalescing
  4. Summary - null & undefined

16 Strict mode

  1. strict: true
  2. strictNullChecks
  3. strictFunctionTypes
  4. Summary - Strict mode

17 Project: Shopping cart

  1. Cart design
  2. Add product
  3. Total calculation
  4. Apply discount
  5. Integration

18 Project: Todo CLI

  1. Task model
  2. Add and list
  3. Completion
  4. Filtering
  5. Integration

19 Project: Library

  1. Book model
  2. Add and search
  3. Borrow
  4. Return
  5. Integration

20 Beginner final

  1. Challenge 1: Types
  2. Challenge 2: Functions
  3. Challenge 3: Unions
  4. Challenge 4: Mini app