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Multidimensional arrays

Learn to define nested arrays.

Multidimensional arrays

A multidimensional array is a structure where an array contains other arrays. The nested array type is written as number[][], meaning "an array of number arrays". It is used for matrix or table-like data.

let matris: number[][] = [
    [1, 2, 3],
    [4, 5, 6]
];
console.log(matris[0][1]);  // 2

Accessing nested elements

To access an element in nested arrays, two brackets are used. matris[0] gives the first row, and matris[0][1] gives the second element of the first row. TypeScript type-checks even when rows and columns differ in count.

let tablo: string[][] = [
    ["ad", "soyad"],
    ["Ali", "Yılmaz"]
];
console.log(tablo[1][0]);  // "Ali"

Practice Number matrix

Define a 2x3 matrix named matris of type number[][]: first row [1, 2, 3], second row [4, 5, 6]. Then print the second row with console.log.

Starter code

index.ts
// 2x3 sayı matrisi tanımla, ikinci satırı yazdır

Sample solution

index.ts
let matris: number[][] = [
    [1, 2, 3],
    [4, 5, 6]
];
console.log(matris[1]);

Expected output

[ 4, 5, 6 ]

Questions and answers

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

1 What does the `string[][]` type express?

  • An outer array whose each element is a string array Correct answer
  • A single string value
  • A readonly string array
  • A fixed set of two strings

Explanation: `string[][]` defines an outer array whose each element is a `string[]`; this creates nested string arrays.

2 Write a nested array type

Question 
let koordinatlar: number____ = [[0, 0], [3, 4]];
Answer 
let koordinatlar: number[][] = [[0, 0], [3, 4]];

Explanation: `number[][]` specifies an array of number arrays; each element must be of type `number[]`.

3 Multidimensional concepts

Term Meaning
number[][] A number matrix
string[][] A string table
matris[0] The first row
matris[0][1] The second element of the first row

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