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Book model

Design book and member types.

Book model

We define three core types for a library. Book represents a book: id, title, author, and available (loan status). Member represents a member: id and name. Library holds an array of books.

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

Empty library

An empty library is a Library object whose books field is an empty array. The array grows as you add books.

const lib: Library = { books: [] };
console.log(lib.books.length);  // 0

Practice Write the library model

Define a Book interface: id: string, title: string, author: string, available: boolean. Define a Member interface: id: string, name: string. Define a Library interface: books: Book[]. Create an empty library and print the number of books.

Starter code

index.ts
// Book arayüzü tanımla (id, title, author, available)
// Member arayüzü tanımla (id, name)
// Library arayüzü tanımla (books alanı Book dizisi)
// boş kütüphane oluştur, kitap 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[]; }

const lib: Library = { books: [] };
console.log(lib.books.length);

Expected output

0

Questions and answers

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

1 Which field tracks whether a book is borrowed?

  • available (boolean) Correct answer
  • title
  • author
  • id

Explanation: The available field is true when the book is on the shelf and false when it is borrowed. title, author, and id do not track loan status.

2 Complete the Book field

Question 
interface Book { id: string; title: string; author: string; ____: boolean; }
Answer 
interface Book { id: string; title: string; author: string; available: boolean; }

Explanation: The Book interface contains an available field; true means on shelf, false means borrowed. count, status, and borrowed are alternative names, but our design uses available.

3 Library model parts

Term Meaning
Book Book details (id, title, author, available)
Member Member details (id, name)
Library Book collection
available: boolean Loan status

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