Basic types, Literal Types

primitive types

let x: number // includes NaN and Infinity
let x: string
let x: boolean
let x: null
let x: undefined
let x: bigint
let x: symbol

loose types (do not use)

The object and {} types are too broad to be useful:

• object covers everything except primitive types, aka plain objects, arrays, functions, sets etc.
• {} covers everything except null or undefined.

let x: object
let x: {}

literal types

The type consists of a single literal:

type T = "unavailable"

union of literals

We create a union of literal types. For example, a union type of string literals:

type T = "unavailable" | "available"