Determine the data type of every element in an array containing a variety of data types

My array contains a mix of values:

const array = [false, 1, '', class T {}];

The type of the array is:

type arrayType = typeof array; // (string | number | boolean | typeof T) []

Each object at an index can have the following types:

string | number | boolean | typeof T

How can I determine the specific type of an object at a given index, rather than a union of types?

const a = array[0] // expected to be boolean
const b = array[1] // expected to be number
const c = array[2] // expected to be string
const d = array[3] // expected to be typeof T

TS Playground

Answer №1

In order to define a tuple type in TypeScript, you have two options: explicitly specify the type or let TypeScript infer it using the as const assertion:

const array = [false, 1, ''] as const;

type arrayType = typeof array; /// readonly [false, 1, ""]

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