TypeScript: Define Types/Interfaces for Multidimensional Arrays

Updated: February 14, 2024 By: Guest Contributor Post a comment


In this tutorial, we will explore how to work with multidimensional arrays in TypeScript by defining types and interfaces for them. A multidimensional array is essentially an array of arrays, and TypeScript’s strong typing system allows us to define the structure and types of these arrays precisely. This can improve the robustness and maintainability of your code.

Understanding Multidimensional Arrays

Before we dive into defining types and interfaces for multidimensional arrays, let’s understand what they are. A multidimensional array, often called a 2D array, is an array where each element is also an array. This structure can be extended to 3D arrays and beyond.

For example, consider a 2D array representing a matrix or a spreadsheet where you have rows and columns:

let matrix: number[][] = [
 [1, 2, 3],
 [4, 5, 6],
 [7, 8, 9]

Defining Types for Multidimensional Arrays

One of the strengths of TypeScript is the ability to define explicit types for various structures, including arrays. For multidimensional arrays, you define the type based on the level of depth the array has.

Basic 2D Array: To define a type for a basic 2D array, you simply use the array type annotation twice.

type TwoDimensionalArray = number[][];

Here, TwoDimensionalArray is a type that represents an array of number arrays.

Fixed Size 2D Array: Sometimes, you might want to enforce a fixed size for your multidimensional arrays. TypeScript allows you to do this by specifying the length of the outer and inner arrays.

type FixedSize2DArray = [[number, number, number], [number, number, number]];

This type enforces a 2×3 matrix where each row has exactly three numbers.

Using Interfaces for Multidimensional Arrays

Interfaces in TypeScript allow for a more structured approach to defining types. They are particularly useful when working with complex data structures.

Interface for 2D Array: You can also use an interface to define a 2D array. This is useful when you want to associate additional properties or methods with the array.

interface TwoDimensionalArrayInterface {
 matrix: number[][];
 getCell(row: number, column: number): number;
 setCell(row: number, column: number, value: number): void;

This interface declares a 2D array alongside methods for getting and setting cell values, illustrating how interfaces can be used to enhance multidimensional arrays with additional functionality.

Typing Multidimensional Arrays with Generics

TypeScript’s generics offer a flexible way to define types for structures whose exact types are not known until they are used. This is particularly useful for creating reusable multidimensional array types.

Generic 2D Array:

type Generic2DArray = T[][];

By utilizing generics, you can define a 2D array type that can be reused for different data types. For example, a 2D array of strings would be defined as Generic2DArray<string>, and a 2D array of numbers would be Generic2DArray<number>.


Defining types and interfaces for multidimensional arrays in TypeScript can greatly enhance the type safety and reliability of your code. Whether you’re dealing with simple 2D arrays or more complex structures, TypeScript’s type system provides the tools you need to clearly define and manage your data.

By understanding how to use types, interfaces, and generics to define multidimensional arrays, you’re better equipped to develop robust and maintainable TypeScript applications. Remember to leverage TypeScript’s type system to its full advantage, making your code more readable and reducing the likelihood of runtime errors.