TypeScript interview questions

Want to become an expert in cracking TypeScript interview questions?

Start with practicing the questions below. Whether a question involves multiple choice or live coding, we will give you hints as you go and tell you if your answers are correct or incorrect.

After that, take our timed public TypeScript interview questions test.

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1. Color Type
TypeScript Arrays OOP Public New

The following code initializes three types representing the colors: red, green and blue.

type ColorType = [string, number, number, number];
let red: ColorType = ['Red', 1, 0, 0];
let green: [string, number, number, number] = ['Green', 0, 1, 0];
let blue = ['Blue', 0, 0, 1];

Select all the statements that are correct.

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2. Uppercase Types
TypeScript Language features OOP Public

The following code initializes strings as three different types and attempts to make them uppercase. Which statements about the behavior of the typescript compiler are correct?

let stringType: string = "string type";

let anyType: any = "any type";

let objectType: Object = "object type";
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3. Positionable
TypeScript Mixins OOP Public New

Consider the following two base classes, Positionable and Rotatable, and MovingObject derived class:

class Positionable {
    locationX: number;
    locationY: number;

class Rotatable {
    orientation: number;
    rotate(orientation: number) {
        this.orientation += orientation;
    align(rotatable: Rotatable) {
        this.orientation = rotatable.orientation;

class MovingObject implements Positionable, Rotatable {
    locationX: number = 0;
    locationY: number = 0;
    orientation: number = 0;
    rotate: (orientation: number) => void;

applyMixins(MovingObject, [Positionable, Rotatable]);
function applyMixins(derivedCtor: any, baseCtors: any[]) {
    baseCtors.forEach(baseCtor => {
        Object.getOwnPropertyNames(baseCtor.prototype).forEach(name => {
            derivedCtor.prototype[name] = baseCtor.prototype[name];

let mover = new MovingObject(); 

Select all the statements that are correct.

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If you feel ready, take one of our timed public TypeScript interview questions tests:

  • Angular and TypeScript (15-min test) ( Easy )
  • TypeScript and JavaScript online test ( Easy )
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