JavaScript Quiz Test Online (30 random Questions) 2026

Improve your JavaScript skills with this online quiz featuring 30 multiple-choice questions. Whether you’re a beginner or an experienced developer, this quiz covers JavaScript fundamentals, functions, objects, DOM manipulation, ES6 features, and asynchronous programming.

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30 Minutes JavaScript Quiz Test Online

Test your JavaScript knowledge with this 30-minute quiz! Covering fundamental to advanced concepts, this quiz features 30 multiple-choice questions that will challenge your understanding of variables, functions, objects, asynchronous programming, and DOM manipulation. Perfect for interview preparation and skill enhancement.

1 / 30

1. What is the default phase of event propagation?

A) None of the above

B) Capturing phase

C) Bubbling phase

D) Target phase

2 / 30

2. How can you handle both the response and errors in the Fetch API?

A) Using catch() only

B) Using then() only

C) Using then() and catch()

D) Using finally()

3 / 30

3. What does the DOMContentLoaded event signify?

A) The document and all resources (images, CSS, etc.) are loaded.

B) The DOM is partially constructed.

C) The DOM is fully constructed.

D) The document and CSS are loaded but not images.

4 / 30

4. Which tool is commonly used for JavaScript testing?

A) Webpack

B) Jest

C) Babel

D) ESLint

5 / 30

5. Which method is used to open a request in XMLHttpRequest?

A) start()

B) open()

C) beginRequest()

D) openRequest()

6 / 30

6. How can you remove an existing child element in the DOM?

A) deleteChild()

B) clearChild()

C) removeElement()

D) removeChild()

7 / 30

7. What is the purpose of minifying JavaScript files?

A) To add comments to the code.

B) To detect syntax errors.

C) To improve code readability.

D) To reduce file size for faster loading.

8 / 30

8. What is the purpose of the window.requestAnimationFrame() method?

A) To create animations.

B) To optimize animations by syncing with the screen refresh rate.

C) To stop animations.

D) To reload the page.

9 / 30

9. Which method is used to parse JSON data in JavaScript?

A) JSON.convert()

B) JSON.parse()

C) JSON.stringify()

D) JSON.read()

10 / 30

10. What does console.assert() do in debugging?

A) Displays debugging information in a separate file.

B) Stops code execution.

C) Throws an error if the condition is false.

D) Logs all variable values.

11 / 30

11. What does the target property of an event object return?

A) The element that triggered the event.

B) The parent element of the event.

C) The default action of the event.

D) The type of the event.

12 / 30

12. How do you create a custom animation using the Web Animations API?

A) Use element.animate() method.

B) Use CSS.animate() method.

C) Use window.createAnimation() method.

D) Use animation.create() method.

13 / 30

13. How can you monitor changes to the size of an element?

A) Using the performance.now() method.

B) Using the MutationObserver API.

C) Using the IntersectionObserver API.

D) Using the ResizeObserver API.

14 / 30

14. What is the purpose of reduce() in JavaScript?

A) Executes a reducer function on each element, resulting in a single output

B) Concatenates arrays

C) Filters elements

D) Reduces array size

15 / 30

15. How do you add a new attribute to an element in JavaScript?

A) element.createAttribute(name, value)

B) element.attribute(name, value)

C) element.setAttribute(name, value)

D) element.addAttribute(name, value)

16 / 30

16. What does setTimeout() do in JavaScript?

A) Executes code repeatedly

B) Stops code execution for a set time

C) Executes a function after a delay

D) Executes a function immediately

17 / 30

17. How can you remove an item from localStorage?

A) localStorage.clearItem()

B) localStorage.eraseItem()

C) localStorage.removeItem()

D) localStorage.delete()

18 / 30

18. What does the window.scrollTo() method do?

A) Scrolls the document to a specific position.

B) Highlights the content on the page.

C) Saves the current scroll position.

D) Adjusts the browser zoom level.

19 / 30

19. Which API is used to make WebSocket connections?

A) WebSocket

B) HTTP

C) fetch()

D) Ajax

20 / 30

20. How do you declare a variable in JavaScript?

A) var

B) All of the above

C) let

D) const

21 / 30

21. What is JavaScript primarily used for?

A) Server-side programming

B) Designing static websites

C) Writing system-level software

D) Adding interactivity to web pages

22 / 30

22. How do you call the parent class constructor in a subclass?

A) parent();

B) constructor();

C) super();

D) base();

23 / 30

23. What does the window.location object represent?

A) The browser's history.

B) The user's geolocation.

C) The URL of the current document.

D) The browser's settings.

24 / 30

24. Which of the following best describes load testing?

A) Testing individual components in isolation.

B) Debugging memory leaks in the code.

C) Testing an application for security vulnerabilities.

D) Measuring the application's performance under high user load.

25 / 30

25. How do you create a new Web Worker in JavaScript?

A) WebWorker()

B) new Worker()

C) createWorker()

D) Worker.create()

26 / 30

26. What is the use of arrow functions in ES6?

A) Declares functions with a simpler syntax

B) All of the above

C) Supports this context binding

D) Declares functions with lexical this binding

27 / 30

27. What is the difference between call() and apply() methods in JavaScript?

A) call() accepts arguments as an array, apply() as separate arguments.

B) Both are used to create new objects.

C) Both are the same in functionality.

D) apply() accepts arguments as an array, call() as separate arguments.

28 / 30

28. What is the purpose of Object.freeze()?

A) To delete an object

B) To inherit properties

C) To make an object immutable

D) To create a prototype

29 / 30

29. What is inheritance in JavaScript?

A) Using multiple objects together

B) Copying one object to another

C) A class receiving properties and methods from another class

D) Defining methods in an object

30 / 30

30. Which company developed JavaScript?

A) Sun Microsystems

B) Microsoft

C) Netscape

D) Google

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