Mastering TypeScript with Marathon Interview Questions 2024

Relative Questions:

Q1. What all types of values a number can store in typescript?

Q2. How will you store a binary or hex value in typescript?

Relative Questions:

Q1. What will be the output of below given code?

let a:boolean = !true;

console.log(!a);

Relative Questions:

Q1. Explain the differences between null and undefined

Q2. When do you need the void data type?

Relative Questions:

Q1. When do you think “any” type is useful in your code?

Relative Questions:

Q1. When does typescript infers the data type?

Relative Questions:

Q1. What is hoisting?

Q2. How does block scope work?

Q3. What is the scope of a variable?

Relative Questions:

Q1. Explain various ways to declare a string variable

Q2. How will you deal with unicode characters?

Q3. Show the syntax to display long unicode characters

Relative Questions:

Q1. What is a Template Literal?

Q2. How will you display a value or an expression inside template string?

Q3. What is the advantage of using template string ?

Relative Questions:

Q1. How can you define your own custom data type?

Q2. What is type alias/aliases?

Relative Questions:

Q1. What is “never” type? Explain with an example?

Q2. What is the difference between “void” and “never” type?

Relative Questions:

Q1. What is the watch mode & how can you run TypeScript Compiler in watch mode?

Relative Questions:

Q1. What is the use of tsconfig.json file? How do you create it?

Q2. What is the use of tsc --init?

Q3. How can you avoid selected files from getting compiled?

Relative Questions:

Q1. What is the purpose of target option in tsconfig.json?

OR

How can you set the compiled file target or compiled file version?

Relative Questions:

Q1. What is the purpose of the “lib” option?

Q2. What will be the default value of “lib” option?

Relative Questions:

Q1. What is the purpose of the Module options?

Q2. How can you compile a file by giving the module setting at the command line (CLI)?

Relative Questions:

Q1. How do you set a separate path for all compiled files? OR What does outDir do?

Q2. What happens to the subfolders of the source folder when you compile the TypeScript project?

Relative Questions:

Q1. How can you compile all '.ts' files in a single bundle of JavaScript code?

Relative Questions:

Q1. What is the purpose of setting the root directory?

Q2. Which value is considered in “outDir” by default if it is not set?

Relative Questions:

Q1. What is removeComments?

Q.2. What is noEmit?

Relative Questions:

Q1. What is a source map file? Explain the advantage of it

Q.2. What is the purpose of mapRoot option?

Q.3. How does mapRoot setting affect the value of sourceMappingURL?

Relative Questions:

Q1. What is the use of “inlineSources”?

Relative Questions:

Q1. What is an array? Explain in detail

Q2. How will you get the last element of the array?

Q3. Get all odd numbers from the array

Relative Questions:

Q1. What is a tuple and how is it different from an array?

Relative Questions:

Q1. How can you define a variable with more than 1 type of data?

Q2. Is it possible to have an array with union data type?

Relative Questions:

Q1. Get sum of a key field of an object literal e.g. the object is

const employees=[

{eNo:1001,salary:3000},

{eNo:1002,salary:2200},

{eNo:1003,salary:3400},

{eNo:1004,salary:6000}

]

Q2. Find avg value of all elements of an array?

Q3. Find the sum or product of all elements?

Q4. What is the difference between reduce() and reduceRight()?

Relative Questions:

Q1. How to flatten a 2D or a multidimensional array?

Relative Questions:

Q1. What is the difference between for..in & for..of?

Relative Questions:

Q1. What will be the output of the code?

       let arr: string[] = ["ES5","ES6","ES7","ES8"];

       arr.forEach((elem, index)=> {

            console.log(elem, index);

            if(index==2){

                 break;

            }

       });

Q2. What will be the output of below statements?

       let arr: number[] = [7,9,0];

       console.log(arr[arr.length]);

Relative Questions:

Q1. What will be the output in case an array has "undefined" while sorting the values?

Q2. How to sort an object literal?

       const employees = [

            {eNo:1001, salary:3000},

            {eNo:1002, salary:2200},

            {eNo:1003, salary:3400},

            {eNo:1004, salary:6000},

      ]

Q3. How will you sort a numeric array?

Q4. Sort all values of array in descending order.

Relative Questions:

Q1. What is the destructuring assignment?

Q2. Swap values using destructuring

Q3. What will be the output of this code?

let [a,b,c] = [5,,7];

console.log(a,b,c);

Q4. How will you set a default value while destructuring an array?

Relative Questions:

Q1. Explain TypeScript function & how is it different from JavaScript?

Relative Questions:

Q1. How do you invoke an anonymous function?

Q2. What will be the output of below given code

        let sum = function(a:number, b:number):number {

            return a+b;

        }

        console.log(typeof sum);

Relative Questions:

Q1. Explain arrow function syntax.

Relative Questions:

Q1. How will you pass default values to a parameter in a function?

Q2. What is the advantage of optional parameter feature?

Relative Questions:

Q1. Create a function which can take any number of values & return sum of all numbers

Q2. Create a function which can take any number of names & displays all names separated with comma

Relative Questions:

Q1. Explain what is a function type?

Relative Questions:

Q1. What is function overloading and how will you implement it?

Relative Questions:

Q1. What is enum and How can you create it in TypeScript?

Q2. Explain advantages of enum.

Q3. What will be the value of WED i.e. Wednesday in below example:

        enum WorkDays{

             MON=1,

             TUE=3,

             WED,

             THU,

             FRI

        }

        console.log(Workdays);

        console.log(Workdays.WED);

Relative Questions:

Q1. Explain computed enum members. Give an example

Relative Questions:

Q1. What is reverse mappings with enum?

Relative Questions:

Q1. Can you have dynamic keys with Object Literal?

Relative Questions:

Q1. How can you add read-only properties to an object?

Relative Questions:

Q1. What will be the output of this code?

       let obj = {a: 'First'};

       let obj1 = obj;

       obj1.a = "Second";

       console.log(obj.a);

Q2. How can we create a clone or separate copy of an Object Literal?

Relative Questions:

Q1. What will be the output of this code if you run it in the browser and why?

       function test() {

            console.log(this);

      }

      test();

Q2. What is the context of "this" inside arrow functions? Or What will be the output of this code?

       let obj = {

          test:()=>{

             console.log(this);

          }

       }

       obj.test();

Relative Questions:

Q1. How will you create a class in TypeScript?

Q2. What is a constructor? How is it called?

Q3. How do you refer to the field/property method of a class?

Q4. How do you access property within the class?

Q5. What do you mean by a member of a class? How many members do you see in this class code?

       class car{

           color: string;

           seats: number;

           constructor(c:string, ns:number) {

                   this.color = c;

                   this.seats = ns;

           }

          buidCar(){

                console.log(this.color, this.seats);

          }

       }

       let c1 = new Car("Red", 2);

       let c2 = new Car("Blue", 4);

       c1.buidCar();

       c2.buidCar();

Relative Questions:

Q1. How do you inherit a class?

Q2. Why do you need the super() method? Explain in detail.

Relative Questions:

Q1. Explain various access modifiers of a class.

Q2. Which is the default access modifier?

Q3. Can you have protected modifier without inheritance?

Relative Questions:

Q1. What are property initialization shorthands?

Relative Questions:

Q1. How will you make a property readonly?

Q2. Can you have a readonly modifier a with public, private or protected modifier?

Q3. make a private property readonly property parameter syntax.

Q4. What is the difference between readonly and const?

Relative Questions:

Q1. How do you make any member static in a class?

Q2. Explain the purpose or advantage of making a member static.

Relative Questions:

Q1. Explain a practical scenario of Object Literal Destructuring.

Q2. Explain the output of this code?

Const {a = 90, b} = {};

Console.log(a,b);

Relative Questions:

Q1. What is an abstract class?

Q2. Can we create a constructor() in an abstract class?

Q3. Is it possible to add instance variables in an abstract class?

Relative Questions:

Q1. What is a getter or setter method?

Relative Questions:

Q1. What is an Interface or Object Types in TypeScript?

Q2. What is the difference between custom types i.e., type & interface?

Relative Questions:

Q1. How can you make sure that a class follows certain signature?

Q2. How do you apply an interface on a class?

Q3. How can you apply multiple interfaces on a class?

Q4. How can you provide an optional property inside an interface?

Relative Questions:

Q1. How can you make properties readonly via interphase?

Relative Questions:

Q1. How will you inherit an interface?

Q2. Can you extend multiple interfaces & how?

Relative Questions:

Q1. What is typescript generics? Explain with syntax

Q2. Is it necessary to pass data type with function call when you call generic function?

Q3. What will be the output of the below given code?

function getData<T>(dataPoints : T[] ) : T[] {

return new Array<T>().concat(dataPoints);

}

let numDP = getData([30,560,120,90]);

let strDP = getData(["Top","Bottom","Left"]);

numDP.push(68);

strDP.push("NE");

numDP.push("Right");

strDP.push(120);

console.log(numDP);

console.log(strDP);

Relative Questions:

Q1. How can you use multiple type variables?

Q2. Is it possible to have generic and non generic types together?

Relative Questions:

Q1. What is Generic Constraint & how we can add it?

Relative Questions:

Q1. How to implement generic classes?

Relative Questions:

Q1. Explain syntax of how to define generic interface

Q2. Give an example of using generic interface as the function type

Relative Questions:

Q1. What is a module?

Q2. Can you import any module inside a script tag?

Q3. How will you run the import and export statements on a local machine?

Relative Questions:

Q1. What is named export & import?

Q2. Can you avoid {} while importing a named module?

Q3. How can you import all named modules from a file?

Q4. Is it a good practice to import all modules together?

Q5. Do the modules hoist?

Q6. Do you need the same name while importing a named module or you can change?

Relative Questions:

Q1. What is default import/export & the difference between named & default import/export?

Q2. Explain various ways of implementing default export & import

Relative Questions:

Q1. How do you deal with modules in TypeScript?

Relative Questions:

Q1. What is namespace? Explain the syntax

Q2. How will you compile multiple namespaces in a single file?

Q3. Explain the syntax of managing nested namespaces

Relative Questions:

Q1. How will you define decorator for a class?

Q2. Explain parameters passed to the decorator function when its applied to the class?

Relative Questions:

Q1. Make a method enumerable with the help of method decorator

Q2. Explain parameter details of method decorator function

Q3. Change method definition using decorator

Relative Questions:

Q1. What is an accessor decorator?

Relative Questions:

Q1. Explain property decorator with syntax.

Q2. Create a property decorator factory which adds a given prefix to the property value.

Relative Questions:

Q1. What is parameter decorators?