Tuples

Tuples

Tuples are fixed-length arrays where each element has a specific type at a specific position.

Basic Tuple

let tup: [string, number, boolean] = ["Mario", 25, true];

tup[0] = "Luigi";  // ✅ string at position 0
tup[0] = 30;       // ❌ Error — must be string at position 0
tup[1] = "hello";  // ❌ Error — must be number at position 1

Tuples vs Arrays

Feature	Array	Tuple
Length	Variable	Fixed
Types	Same type (or union)	Specific type per position
Order	Any order	Fixed order

Named Tuples (TS 4.0+)

type User = [name: string, age: number, active: boolean];
const user: User = ["Mario", 30, true];

Practical Use Case

// CSV row data
type CsvRow = [string, number, boolean];

const data: CsvRow[] = [
    ["Mario", 30, true],
    ["Luigi", 28, false],
    ["Peach", 25, true],
];

// Destructuring tuples
const [name, age, active] = data[0];
console.log(name);  // "Mario"

Readonly Tuples

const coords: readonly [number, number] = [10, 20];
coords[0] = 30;  // ❌ Error — readonly

Key Takeaways

• Tuples have fixed length and typed positions
• Each position must match its declared type
• Great for CSV data, coordinates, and function returns
• Named tuples improve readability