In JavaScript we have two categories of types.
Primitive types
boolean number string symbol bigInt null undefined
Complex types
object array
TypeScript allows us to use kind new of types.
Enum
To put it simply it is a collection of named values (See Enums in JavaScript). In TypeScript enums are by default numbers starting from 0.
//
enum Suit { Spades, Hearts, Diamonds }
const suit: Suit = Suit.Spades //0
//
We can also define enums in the normal way, with key and values.
//
enum UserRole = { Admin = 'admin', User = 'user' };
const userRole = UserRole.Admin //admin
//
Tuple
It represents an array with defined number of elements and their types.
// const tuple1: [number, string] = [1, ‘John’]; const tuple2: [firstName: string, age: number, value: number] //
Union
When the type specified more than one data type.
// let uniqID: (string | number); code = 123; // Good code = 'e12030'; // Good code = false; // Error //
Void
Means “no value”. We can use it for example for functions that will return nothing.
//
function helloWorld(): void {
console.log('Hello World!')
}
//
Object
It is mainly used for other types to inherit from it.
Never
A special type, describes a value that will never occur (for example when you want to throw a new Error function).
//
function throwError(error: string): never {
throw new Error(error);
}
//
Any
Means any type. Not recommend to use.
Unknown
Represents a type that is unknown. It is safer than any type because we cannot use this as often as any.