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Tuple ↔ Array with fixed length & fixed element Type

Tuple Type used to distinguish from Array Literal which TSC infers as List

Tuple useful for reping ordered sequence of elements ie CSV files

Variadic Tuple​

Tuple Type Annotation using Spread Operator or Rest Parameter, to define varying number of element types

let xy: [number, number] = [1, 2];

otherwise TSC infers Type as number[]

const entries: [string, number][] = Object.entries({ x: 1, y: 2})

Object.entries() returns an array of tuples: [["a", 1], ["b", 2]]

const drink_obj = {color: "brown", carbonated: true, sugar: 40}
const drink_tup = [brown, true, 40]

Convert the following array into a tuple:

const pepsi = ["brown", true, 40]

via type annotation: const pepsi: [string, boolean, number] = ["brown", true, 40]; via type alias: type Drink = [string, boolean, number]; const pepsi: Drink = ["brown", true, 40];

References​

  1. Variadic Tuple ↔ Tuple Type Annotation using Spread Operator or Rest Parameter, to define varying number of element types