Arrays and Tuples in TypeScript¶

Arrays¶

Arrays store multiple values of the same type.

let numbers: number[] = [1, 2, 3, 4]

let names: string[] = ["Aman", "Rahul", "Priya"]

Alternative syntax:

let numbers: Array<number> = [1, 2, 3]

let nums: number[] = [10, 20, 30]

console.log(nums[0]) // 10
console.log(nums[2]) // 30

TypeScript supports normal JavaScript array methods but enforces type safety.

let numbers: number[] = [1, 2, 3]

numbers.push(4)      // valid
numbers.push(5)

numbers.push("6")    // error

let fruits: string[] = ["apple", "banana", "mango"]

for (let fruit of fruits) {
  console.log(fruit)
}

Prevents modification.

let nums: readonly number[] = [1, 2, 3]

nums.push(4)   // error
nums[0] = 10   // error

Alternative:

let nums: ReadonlyArray<number> = [1, 2, 3]

Tuples are arrays with fixed length and specific types at each position.

Example: a user with id, name, and active status.

let user: [number, string, boolean] = [1, "Aman", true]

Index meaning:

let user: [number, string] = [101, "Aman"]

console.log(user[0]) // 101
console.log(user[1]) // Aman

let user: [number, string, boolean?]

user = [1, "Aman"]
user = [1, "Aman", true]

let data: [number, ...string[]]

data = [1, "a", "b", "c"]

First element must be a number, remaining must be strings.

let user: [id: number, name: string]

user = [1, "Aman"]

Example comparison:

let scores: number[] = [90, 85, 88]

let student: [number, string] = [1, "Aman"]

let point: [number, number] = [10, 20]

let response: [number, string] = [200, "Success"]

let color: [number, number, number] = [255, 0, 0]