type alias

readonly

type User = { readonly _id: string name: string email: string isActive: boolean }

never

void

array

• let myNumbers: number[] = [1, 2, 3]
• const myNumbers2: Array = [1, 2, 3]

type User2 = { name: string age: number }

• let users: User2[] = []

union

• let score: number

  string = 33

tuple

• let user: [number, string] = [1, ‘adarsh’]

enum

enum Size { Small = ‘s’, Medium = ‘m’, Large = ‘l’, } let mySize: Size = Size.Medium console.log(mySize) // ‘m’

enum vs const enum

• enum: values are real objects that exist at runtime
• const enum: completely removed during compilation

interface

interface User3 {
  name: string
  age: number
}

let user3: User3 = { name: ‘adarsh’, age: 22 }

extend interface interface User4 extends User3 { role: string } also reopenable interface User4 { isActive: boolean } let user4: User4 = { name: ‘adarsh’, age: 22, role: ‘admin’, isActive: true }