Typescript

Question 1

var, let, const

Answer 1

var is function scoped
let & const is block scoped

var width:number = 100;
let height:number = 200;
const key:string = ‘abc123’;

Question 2

scope of var

Answer 2

function

Question 3

scope of let

Answer 3

block scope

Question 4

scope of const

Answer 4

block scope

Question 5

Basic types / Non-Basic-types

Answer 5

boolean
number
string
numer[] or Array
enum
---------
any
never
void

Question 6

initialize an enum

Answer 6

Zero-Index

enum Color {Red, Green, Blue};
let c: Color = Color.Green;

Question 7

initialize an Array

Answer 7

let aArray: number[] = [1, 2, 3];

let aGenericArray: Array = [4,5,6];

Question 8

never

Answer 8

never is used when a function never returns. e.g. it’s in a loop or always throws an exception.

Question 9

Modifier

Answer 9

public
protected
private
readonly

Question 10

Duck Typing

Answer 10

Compiler kann den Type selbst ableiten

Question 11

Fat Arrow Function

Answer 11

(param1, param2, …, paramN) => expression

let sum = (x: number, y: number): number => {
    return x + y;
}

Question 12

Generic example

Answer 12

interface Identity { id: string; }

class Movie implements Identity {
  id: string;
}

function getAsync(arg: T): Promise {
  return fetch(`/api/${arg.id}`)
    .then((response: Response) => >response.json());
}

Question 13

Diamond Operator

Answer 13

<>