In TypeScript, arrays are a collection of elements of the same type (or a union of types). TypeScript enforces type safety, ensuring that the array only contains elements of the specified type.

Defining Arrays in TypeScript

1. Using the Array Generic:

   typescript
   let arrayName: Array<Type>;
   

2. Using Square Bracket Notation:

   typescript
   let arrayName: Type[];
   

Examples

1. Single-Type Arrays

typescript
// Using Array Genericlet numbers: Array<number> = [1, 2, 3];// Using Square Bracket Notationlet strings: string[] = ["apple", "banana", "cherry"];

2. Union-Type Arrays

typescript
let mixed: (number | string)[] = [1, "two", 3, "four"];

3. Readonly Arrays

Readonly arrays prevent modification of their elements.

typescript
let readonlyNumbers: ReadonlyArray<number> = [1, 2, 3];// readonlyNumbers.push(4); // Error: Cannot modify a readonly array

Array Operations in TypeScript

TypeScript supports standard array methods such as push, pop, map, filter, and more.

Example:

typescript
let numbers: number[] = [1, 2, 3, 4];// Add an elementnumbers.push(5);// Remove the last elementnumbers.pop();// Map over the arraylet doubled = numbers.map((n) => n * 2); // [2, 4, 6, 8]// Filter the arraylet evenNumbers = numbers.filter((n) => n % 2 === 0); // [2, 4]

Special Array Types

1. Tuples

Tuples are fixed-length arrays where each element can have a different type.

typescript
let tuple: [string, number, boolean] = ["Alice", 25, true];

2. Multi-Dimensional Arrays

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

3. Arrays with Optional Elements

typescript
let optionalArray: (number | undefined)[] = [1, undefined, 3];

Type Checking and Inference

TypeScript infers the type of an array if initialized with values:

typescript
let inferredArray = [1, 2, 3]; // inferred as number[]

You can also explicitly declare the type to avoid inference issues:

typescript
let explicitArray: string[] = ["hello", "world"];

Examples of Common Use Cases

1. Looping Through Arrays

typescript
let fruits: string[] = ["apple", "banana", "cherry"];for (let fruit of fruits) {  console.log(fruit);}fruits.forEach((fruit) => console.log(fruit));

2. Function Parameters and Return Types

typescript
function getFirstElement(arr: number[]): number | undefined {  return arr[0];}let first = getFirstElement([10, 20, 30]); // 10

TypeScript vs JavaScript Arrays

• Type Safety: TypeScript enforces that the array elements match the specified type.
• Readonly Feature: TypeScript allows defining arrays as readonly.
• Advanced Types: Supports tuples, union types, and intersections for arrays.