typescript

 Type script:

//union type

let course: string | number = 'Complete guide';

course = 1234;

//type alias

type Person = {

name: string,

age: number;

}

let person: Person;

//generics

function insertAtBeginning(origArray: any[],value: any){

const newArray = [value,...origArray];

return newArray;

}

const demoArray = [1,2,3];

const upadtedArray = insertAtBeginning(demoArray,-1);

upadtedArray[0].split('');

//to

function insertAtBeginning2<T>(origArray: T[],value: T){

const newArray = [value,...origArray];

return newArray;

}

const demoArray2 = [1,2,3];

const upadtedArray2 = insertAtBeginning2(demoArray,-1);

upadtedArray2[0].split(''); //error detected

let idStr: string = "2";

const id = +idStr;

console.log(id*8);

this.isAuthenticated = !user : false : true;

equals

this.isAuthenticated = !!user;