Programming with Types

Types and possible values

Name [Section]	TypeScript type	Possible values
Empty type [2.1.1]	never	No possible values
Unit type [2.1.2]	void	One possible value
Sum type [3.4.2]	number | string	A value from number or a value from string
Tuple (product type) [3.1.1]	[number, string]	A value from number and a value from string
Record (product type) [3.1.2]	{ a: number; b: string; }	A (named) value from number and a (named) value from string
Function type [5.1.2]	(value: number) => string	A function number → string
Top type [7.2.1]	unknown	A value of any type
Bottom type [7.2.2]	never	No possible values (the bottom type is the subtype of any other type)
Interface [8.1]	interface ILogger { /* ... */ }	Object of a ...