Javascript Mock Test | TNP Officer

Q: What types of questions are asked in JavaScript interviews?

JavaScript interviews typically include: Theoretical questions (e.g., Explain closures, prototypal inheritance, event delegation). Code debugging (e.g., Find the output of a given JavaScript snippet). Coding challenges (e.g., Reverse a string, find duplicate elements in an array). System design (for advanced roles, e.g., How would you design a real-time chat app using JavaScript?).

Q: How can I prepare for JavaScript interviews effectively?

Start by taking mock tests to evaluate your current knowledge. Solve JavaScript problems daily on platforms like LeetCode. Learn common interview patterns such as recursion, two-pointer technique, and dynamic programming. Read JavaScript documentation and stay updated with the latest features.

Q: How important is JavaScript in technical interviews?

For frontend roles, JavaScript is crucial as it powers web interactivity. For full-stack roles, knowledge of Node.js is essential. Many companies evaluate problem-solving abilities using JavaScript.

Q: How can I improve my JavaScript problem-solving skills?

Take structured mock tests to simulate real interviews. Break problems down into smaller steps before coding. Understand the time complexity of your solutions. Review past interview questions from companies like Google, Accenture, and TCS.

Free JavaScript Mock Test: Placement

Practice the free Online JavaScript Test to get success in future placement. This interactive MCQ-based online mock test will help you in the time of final placements. Explore a wide range of topics all curated to boost your problem-solving abilities.

JavaScript is one of the most in-demand programming languages, widely used in frontend and backend development. Cracking a JavaScript interview at top companies like Google, Amazon, TCS, and Accenture requires a deep understanding of concepts, problem-solving skills, and hands-on coding experience.

At Tnpofficer.com, we provide comprehensive JavaScript mock tests designed to help you assess your skills and prepare for real-world technical interviews.

General Instructions

1. Each JavaScript test contains 15 questions.
2. Total allotted time is 20 minutes for each test.
3. No negative marking.
4. Try to finish it on time.
5. The Test will be submitted automatically if the time expired.
6. Don’t refresh the page.

JavaScript Test 2

1 / 15

Which of the following is used to iterate over the properties of an object?

A. for…of

B. forEach

C. for…in

D. map

2 / 15

What is the output of the following code?

console.log("5" - 3);

A. "53"

B. NaN

C. 2

D. "2"

3 / 15

What is the output of the following code?

let arr = [1, 2, 3];
arr.length = 0;
console.log(arr);

A. [1, 2, 3]

B. [undefined, undefined, undefined]

C. []

D. [0]

4 / 15

What is the output of the following code?

console.log(typeof []);

A. "array"

B. "object"

C. "null"

D. "undefined"

5 / 15

Which of the following is not a valid way to create an object in JavaScript?

A. let obj = Object.create(null);

B. let obj = {};

C. let obj = Object();

D. let obj = new Object();

6 / 15

Which of the following is used to check if a variable is an array?

A. typeof

B. Array.isArray()

C. instanceof

D. isArray()

7 / 15

Which of the following is used to remove whitespace from the beginning and end of a string?

A. trim()

B. strip()

C. clean()

D. removeWhitespace()

8 / 15

Which of the following is used to handle errors in JavaScript?

A. All of the above

B. try…catch

C. throw

D. finally

9 / 15

Which of the following is used to convert a string to a number?

A. parseInt()

B. parseFloat()

C. All of the above

D. Number()

10 / 15

What is the output of the following code?

let x = 10;
let y = x;
y = 20;
console.log(x);

A. undefined

B. 20

C. 10

D. null

11 / 15

Which of the following is not a valid JavaScript event?

A. onchange

B. onload

C. onhover

D. onclick

12 / 15

What is the output of the following code?

console.log(1 < 2 < 3);
console.log(3 > 2 > 1);

A. false, true

B. false, false

C. true, false

D. true, true

13 / 15

What is the output of the following code?

console.log(typeof undefined);

A. "string"

B. "null"

C. "undefined"

D. "object"

14 / 15

What is the output of the following code?

let x = 5; let y = "5"; console.log(x == y); console.log(x === y);

A. false, false

B. true, false

C. true, true

D. false, true

15 / 15

What is the output of the following code?

let x = 10;
function test() {
  console.log(x);
  let x = 20;
}
test();

A. 10

B. undefined

C. ReferenceError

D. 20

Your score is

The average score is 10%

JavaScript Test 3

1 / 15

What is the output of the following code?

console.log([] + []);

A. "undefined"

B. "0"

C. "[]"

D. ""

2 / 15

Which of the following is not a valid JavaScript loop?

A. do...while

B. for

C. while

D. foreach

3 / 15

What is the output of the following code?

console.log(typeof null);

A. "object"

B. "boolean"

C. "null"

D. "undefined"

4 / 15

Which of the following is not a valid JavaScript data type?

A. Symbol

B. Float

C. BigInt

D. Boolean

5 / 15

Which of the following is used to handle asynchronous operations in JavaScript?

A. setTimeout

B. All of the above

C. async/await

D. Promise

6 / 15

What is the output of the following code?

console.log(0 == false);
console.log(0 === false);

A. false, false

B. true, false

C. true, true

D. false, true

7 / 15

What is the output of the following code?

let x = 5;
console.log(x++);
console.log(++x);

A. 5, 6

B. 6, 6

C. 5, 7

D. 6, 7

8 / 15

Which of the following is used to check if a property exists in an object?

A. hasOwnProperty()

B. includes()

C. Both A and B

D. in

9 / 15

What is the output of the following code?

let arr = [1, 2, 3];
arr[10] = 99;
console.log(arr.length);

A. 3

B. 10

C. 99

D. 11

10 / 15

Which method is used to add an element to the end of an array?

A. push()

B. shift()

C. unshift()

D. pop()

11 / 15

Which of the following is used to execute a function after a specified delay?

A. setInterval()

B. delay()

C. setTimeout()

D. wait()

12 / 15

What is the output of the following code?

let x = 10;
function test() {
  console.log(x);
  var x = 20;
}
test();

A. 10

B. ReferenceError

C. 20

D. undefined

13 / 15

What is the output of the following code?

A. 3

B. "21"

C. 21

D. "3"

14 / 15

Which of the following is used to merge two or more arrays?

A. concat()

B. join()

C. combine()

D. merge()

15 / 15

What is the output of the following code?

let a = 10;
let b = a;
b = 20;
console.log(a);

A. null

B. undefined

C. 10

D. 20

Your score is

The average score is 7%

JavaScript Test 4

1 / 15

What is the output of the following code?

console.log("5" - 3);

A. "53"

B. "2"

C. NaN

D. 2

2 / 15

What is the output of the following code?

console.log([] + []);

A. "undefined"

B. "[]"

C. ""

D. "0"

3 / 15

Which of the following is not a valid JavaScript data type?

A. Symbol

B. Float

C. Boolean

D. BigInt

4 / 15

Which method is used to add an element to the end of an array?

A. pop()

B. push()

C. shift()

D. unshift()

5 / 15

Which of the following is used to execute a function after a specified delay?

A. setInterval()

B. setTimeout()

C. wait()

D. delay()

6 / 15

What is the output of the following code?

console.log(typeof undefined);

A. "undefined"

B. "null"

C. "object"

D. "string"

7 / 15

Which of the following is used to merge two or more arrays?

A. combine()

B. concat()

C. merge()

D. join()

8 / 15

Which of the following is used to check if a variable is an array?

A. typeof

B. instanceof

C. Array.isArray()

D. isArray()

9 / 15

What is the output of the following code?

console.log(typeof null);

A. "undefined"

B. "null"

C. "boolean"

D. "object"

10 / 15

What is the output of the following code?

let x = 10;
function test() {
  console.log(x);
 let x = 20;
}
test();

A. ReferenceError

B. undefined

C. 20

D. 10

11 / 15

Which of the following is not a valid way to create an object in JavaScript?

A. let obj = new Object();

B. let obj = Object.create(null);

C. let obj = {};

D. let obj = Object();

12 / 15

What is the output of the following code?

let arr = [1, 2, 3];
arr[10] = 99;
console.log(arr.length)

A. 11

B. 99

C. 10

D. 3

13 / 15

What is the output of the following code?

let x = 10;
function test() {
  console.log(x);
  var x = 20;
}
test();

A. 20

B. ReferenceError

C. undefined

D. 10

14 / 15

What is the output of the following code?

console.log(2 + "2" - 1);

A. "21"

B. 3

C. 21

D. "3"

15 / 15

Which of the following is used to check if a property exists in an object?

A. in

B. Both A and B

C. hasOwnProperty()

D. includes()

Your score is

The average score is 0%

JavaScript Test 5

1 / 15

What is the output of the following code?

let x = 5;
let y = "5";
console.log(x == y);
console.log(x === y);

A. true, true

B. false, false

C. false, true

D. true, false

2 / 15

What is the output of the following code?

let arr = [1, 2, 3];
arr.length = 0;
console.log(arr);

A. []

B. [undefined, undefined, undefined]

C. [1, 2, 3]

D. [0]

3 / 15

Which of the following is used to check if a variable is an array?

A. isArray()

B. instanceof

C. Array.isArray()

D. typeof

4 / 15

What is the output of the following code?

console.log("5" - 3);

A. "53"

B. 2

C. "2"

D. NaN

5 / 15

Which of the following is used to iterate over the properties of an object?

A. forEach

B. map

C. for...in

D. for...of

6 / 15

Which of the following is not a valid way to create an object in JavaScript?

A. let obj = Object();

B. let obj = Object.create(null);

C. let obj = {};

D. let obj = new Object();

7 / 15

Which of the following is used to convert a string to lowercase?

A. lowerCase()

B. toLower()

C. toLowerCase()

D. convertLower()

8 / 15

Which of the following is used to handle asynchronous operations in JavaScript?

A. async/await

B. setTimeout

C. All of the above

D. Promise

9 / 15

What is the output of the following code?

let x = 5;
console.log(x++);
console.log(++x);

A. 6, 7

B. 6, 6

C. 5, 7

D. 5, 6

10 / 15

What is the output of the following code?

let a = 10;
let b = a;
b = 20;
console.log(a);

A. undefined

B. null

C. 10

D. 20

11 / 15

What is the output of the following code?

console.log(typeof undefined);

A. "string"

B. "object"

C. "undefined"

D. "null"

12 / 15

What is the output of the following code?

console.log(0 == false);
console.log(0 === false);

A. true, false

B. true, true

C. false, true

D. false, false

13 / 15

Which of the following is not a valid JavaScript loop?

A. do...while

B. while

C. for

D. foreach

14 / 15

What is the output of the following code?

let x = 10;
function test() {
  console.log(x);
  let x = 20;
}
test();

A. undefined

B. ReferenceError

C. 20

D. 10

15 / 15

What is the output of the following code?

let x = 10;
let y = (x > 5) && (x < 15);
console.log(y);

A. 15

B. true

C. false

D. 10

Your score is

The average score is 0%

Why You Should Take JavaScript Mock Tests?

Assess Your Knowledge – Identify your strengths and areas for improvement
Get Familiar with Interview Patterns – Our questions are designed to match real interview formats.
Time Management – Practice solving problems under timed conditions
Learn with Explanations – Every question comes with a detailed explanation to enhance understanding.
Boost Confidence – Gain the confidence to face JavaScript interviews with ease.

JavaScript Interview Preparation Tips

Understand the Fundamentals
- Master core concepts like variables, functions, closures, promises, and the event loop.
- Learn ES6+ features such as let, const, arrow functions, and async/await.
Practice Coding Challenges
- Solve problems on data structures (arrays, objects, maps, sets) and algorithms (sorting, recursion).
- Use platforms like LeetCode, CodeSignal, and our JavaScript mock tests to refine your skills.
Work on Real-World Scenarios
- Debug JavaScript code and identify logical errors.
- Practice writing optimized code that performs efficiently.
Mock Interviews & Time Management
- Take our timed JavaScript mock tests to simulate real interview conditions.
- Practice explaining your solutions clearly to build communication skills.

What types of questions are asked in JavaScript interviews?

JavaScript interviews typically include:

Theoretical questions (e.g., Explain closures, prototypal inheritance, event delegation).
Code debugging (e.g., Find the output of a given JavaScript snippet).
Coding challenges (e.g., Reverse a string, find duplicate elements in an array).

System design (for advanced roles, e.g., How would you design a real-time chat app using JavaScript?).

What is the difference between a front-end developer and a full stack developer?

Front-end can be thought of as client-side, while back-end is server-side. HTML, CSS, and JavaScript are the fundamental languages used in front-end development. The user interface is the front-end developer’s primary duty. The back-end developer decides how the website will work.

How can I prepare for JavaScript interviews effectively?

Start by taking mock tests to evaluate your current knowledge.
Solve JavaScript problems daily on platforms like LeetCode.
Learn common interview patterns such as recursion, two-pointer technique, and dynamic programming.
Read JavaScript documentation and stay updated with the latest features.

What is the need of learning front end development?

As the backbone of the online user experience, front-end development is an essential competency for developers looking to further their careers. Learning front-end skills enables people to develop engaging, aesthetically pleasing interfaces that successfully engage users. It facilitates the creation of easily navigable responsive layouts.

How important is JavaScript in technical interviews?

For frontend roles, JavaScript is crucial as it powers web interactivity. For full-stack roles, knowledge of Node.js is essential. Many companies evaluate problem-solving abilities using JavaScript.

How can I improve my JavaScript problem-solving skills?

Take structured mock tests to simulate real interviews.
Break problems down into smaller steps before coding.
Understand the time complexity of your solutions.

Review past interview questions from companies like Google, Accenture, and TCS.