Basics

Variables

let greetings: string = "Hello Hitesh";

greetings.toLowerCase();
console.log(greetings);

let userId = 334455.3;
userId.toFixed();

let isLoggedIn: boolean = false;

let hero: string;

function getHero(){
    return "thor";
}

hero = getHero();

export {};

Array

const superHeroes: string[] = [];
// const heroPower: number[] = [];
const heroPower: Array<number> = [];

type User = {
    name: string;
    isActive: boolean;
}

const allUsers: User[] = [];

const MLModels: number[][] = [[255, 255, 255], []];

superHeroes.push("Spiderman");
heroPower.push(200);

allUsers.push({name: "", isActive: true});

Enums

enum SeatChoice {
    AISLE = "aisle",
    MIDDLE = 3,
    WINDOW,
    FOURTH
}
const hcSeat = SeatChoice.AISLE;

Functions

function addTwo(num: number): number{
    return num + 2;
}

function getUpper(val: string){
    return val.toUpperCase();
}

function loginUser(name: string, email: string, isPaid: boolean) => {};

let myValue = addTwo(5);
getUpper("hitesh");
signUpUser("hitesh", "hitesh@1co.dev", false);
loginUser("h", "h@h.com");

function getValue(myVal: number): boolean{
    if(myVal > 5){
        return true;
    }
    return false;
    // return "200 Ok"
}

const getHello = (s: string): string => {
    return "";
}

const heroes = ["thor", "spiderman", "ironman"];

heroes.map((hero) => string => {
    return `hero is ${string}`;
})

function consoleError(errmsg: string): void{
    console.log(errmsg);
}

function handleErr(errmsg: string): never{
    throw new Error(errmsg);
}


export {};

Interfaces

interface User {
    readonly dbId: number;
    email: string;
    userId: string;
    googleId?: string;
    startTrail(): string;
    getCoupon(couponname: string, value: number):number
}

interface User {
    githubtoken: string;
}

interface Admin extends User {
    role: "admin" | "ts" | "learner";
}

const hitesh: Admin = {dbId: 22, email: "h@h.com",
    userId: 2211,
    role: "admin",
    githubtoken: "github",
    startTrail: () => {
        return 'trail started'
    },

    getCoupon: (name: "hitesh10", off: 10) => {
        return 10;
    }
}

hitesh.email = "h@h.com";

Objects

// const User = {
//     name: "hitesh",
//     email: "hitesh@lo.dev",
//     isActive: true,
// }

// function createUser({name: string, isPaid: boolean}){};

// let newUser = {name:"hitesh", isPaid:true, email: "h@h.com"};

// createUser(newUser);

// function createCourse():{name: string, price: number}{
//     return {name: "reactJs", price: 399};
// }

// type User = {
//     name: string;
//     email: string;
//     isActive:  boolean;
// }

// function createUser(user: User): User{
//     return {name: "", email: "", isActive: true}
// }

// createUser({name:"", email:"", isActive: true});

type User = {
    readonly _id: string;
    name: string;
    email: string;
    isActive: boolean;
    credcardDetails?: number;
}


let myUser: User = {
    _id: "1234",
    name: "h",
    email: "h@h.com",
    isActive: false,
}

type cardNumber = {
    cardNumber: string;
}

type cardDate = {
    cardDate: string;
}

type cardDetails = cardNumber & cardDate & {
    cvv: number;
}

myUser.email = "h@gmail.com";
// myUser._id = "asa";

export {}

Tuples

let tUser: [string, number, boolean];

tUser = ["name", 1, true];

let rgb: [number, number, number] = [255, 123, 112];

type User = [number, string];

const newUser: User = [112, "example@google.com"];

newUser[1] = "hc.com";
newUser.push(true);

Unions

let socre: number | string = 33;
socre = 44;
socre = "55";

type User = {
    name: string;
    id: number;
}

type Admin = {
    username: string;
    id: number;
}

let hitesh: User | Admin = {name: "hitesh", id: 334};

hitesh = {username: 'hc', id: 334};

// function getDbId(id: number | number){
//     console.log(`DB id is: ${id}`);
// }

getDbId(3);
getDbId("3");

function getDbId(id: number | string){
    if(typeof id === "string"){
        id.toLowerCase();
    }
}

const data: number[] = [1, 2, 3];
const data2: string[] = ["1", "2", "3"];
const data3: (string | number | boolean)[] = ["1", "2", 3, true];

let seatAllotment: "aisle" | "middle" | "window";
seatAllotment = "crewel";