Basic intro to TypeScript (From YouTube Crash Course)

typescript-crash.ts

// Basic Types
let id: number = 5
let company: string = 'Traversy Media'
let isPublished: boolean = true
let x: any = 'Hello'

let ids: number[] = [1, 2, 3, 4, 5]
let arr: any[] = [1, true, 'Hello']

// Tuple
let person: [number, string, boolean] = [1, 'Brad', true]
// Tuple Array
let employees: [number, string][]

employee = [
  [1, 'Brad'],
  [2, 'John'],
  [3, 'Jill'],
]

// Union
let pid: string | number
pid = '22'

// Enum
enum Direction1 {
  Up = 1,
  Down,
  Left,
  Right,
}

enum Direction2 {
  Up = 'Up',
  Down = 'Down',
  Left = 'Left',
  Right = 'Right',
}

// Objects
type User = {
  id: number
  name: string
}

const user: User = {
  id: 1,
  name: 'John',
}

// Type Assertion
let cid: any = 1
// let customerId = <number>cid
let customerId = cid as number

// Functions
function addNum(x: number, y: number): number {
  return x + y
}

// Void
function log(message: string | number): void {
  console.log(message)
}

// Interfaces
interface UserInterface {
  readonly id: number
  name: string
  age?: number
}

const user1: UserInterface = {
  id: 1,
  name: 'John',
}

interface MathFunc {
  (x: number, y: number): number
}

const add: MathFunc = (x: number, y: number): number => x + y
const sub: MathFunc = (x: number, y: number): number => x - y

interface PersonInterface {
  id: number
  name: string
  register(): string
}

// Classes
class Person implements PersonInterface {
  id: number
  name: string

  constructor(id: number, name: string) {
    this.id = id
    this.name = name
  }

  register() {
    return `${this.name} is now registered`
  }
}

const brad = new Person(1, 'Brad Traversy')
const mike = new Person(2, 'Mike Jordan')

// Subclasses
class Employee extends Person {
  position: string

  constructor(id: number, name: string, position: string) {
    super(id, name)
    this.position = position
  }
}

const emp = new Employee(3, 'Shawn', 'Developer')

// Generics
function getArray<T>(items: T[]): T[] {
  return new Array().concat(items)
}

let numArray = getArray<number>([1, 2, 3, 4])
let strArray = getArray<string>(['brad', 'John', 'Jill'])

strArray.push(1) // Throws error

Thanks, Brad!!! 🙌🏽

best TS review cheatsheet

line 15 is employees

thanks

Thank you!

Thank you!

Thanks Brad

Thanks fot he course man!

Thanks Brad

Thank you brother, very helpfull

Good Work Brad!

thank you

thanks, very helpful!

2023/05/06 I was here . Thanks

Thank you
7.21.23 # 9.13AM

thank you!!

its a good way to start ts!!!!Thank you brad

Thanks aLOT Brad!

Thanks a lot

Thank you... 👍

Thank you Brad! appreciate your work

Thank you!!

cool

Thanks! Really useful video and gist.

Thank you