JavaScript Quiz Test Online (30 Questions) 2025

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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45 Minutes JavaScript Quiz Test Online

Test your JavaScript knowledge with this 45-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. Which method is used to add an element to the end of an array?

A) pop()

B) push()

C) splice()

D) unshift()

2 / 30

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

A) Saves the current scroll position.

B) Scrolls the document to a specific position.

C) Highlights the content on the page.

D) Adjusts the browser zoom level.

3 / 30

3. Which is NOT true about Promise.finally()?

A) It can be used for cleanup.

B) It executes after the promise is settled.

C) It runs only on a rejected promise.

D) It does not modify the resolved value.

4 / 30

4. What is polymorphism in JavaScript?

A) Having multiple methods with the same name but different implementations

B) None of the above

C) Creating multiple instances of a class

D) Inheriting properties from multiple classes

5 / 30

5. Which operator is used to check for inequality in JavaScript?

A) Both A and B

B) !==

C) None of the above

D) !=

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6. What happens if you call stopPropagation() inside a capturing phase listener?

A) The event continues in the bubbling phase.

B) The event is ignored entirely.

C) Only the target element receives the event.

D) The event propagation stops completely.

7 / 30

7. How can you detect if an element has focus?

A) document.hasFocus()

B) element.isFocused()

C) document.activeElement === element

D) element.focused

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8. How do you check if a property exists in an object?

A) Both A and C

B) obj.property

C) property in obj

D) obj.hasOwnProperty(property)

9 / 30

9. How do you create a new promise?

A) Promise.create()

B) new Promise()

C) Promise.start()

D) new Async()

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10. What is the purpose of the AbortController API in JavaScript?

A) To cancel asynchronous operations like fetch().

B) To halt DOM rendering.

C) To clear browser history.

D) To stop animations on a webpage.

11 / 30

11. What does the fetch() method do?

A) Fetches variables from memory

B) Executes functions asynchronously

C) Sends HTTP requests and returns a promise

D) Creates DOM elements

12 / 30

12. What does querySelector() do?

A) Selects elements by ID only.

B) Selects the first matching element.

C) Selects elements by class only.

D) Selects all elements of a given type.

13 / 30

13. What is the purpose of Promise.all()?

A) Resolves multiple promises concurrently

B) Resolves multiple promises sequentially

C) Creates a single promise

D) Rejects all promises if one fails

14 / 30

14. What does Object.assign() do?

A) Creates an object reference

B) Copies values from one object to another

C) Declares an object

D) Merges two arrays

15 / 30

15. What is the result of the code console.log(typeof NaN);?

A) "NaN"

B) "undefined"

C) "object"

D) "number"

16 / 30

16. What is the default state of a JavaScript promise?

A) Resolved

B) Rejected

C) Pending

D) Fulfilled

17 / 30

17. Which property is used to access or change the content of an HTML element?

A) outerHTML

B) innerText

C) innerHTML

D) innerContent

18 / 30

18. How do you toggle a class on an element?

A) element.toggle(className)

B) element.switchClass(className)

C) element.classList.toggle(className)

D) element.classToggle(className)

19 / 30

19. What is JavaScript primarily used for?

A) Designing static websites

B) Server-side programming

C) Adding interactivity to web pages

D) Writing system-level software

20 / 30

20. What does the IntersectionObserver API do?

A) Tracks visibility of elements within the viewport.

B) Monitors resizing of elements.

C) Observes HTTP requests.

D) Observes changes to DOM nodes.

21 / 30

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

A) openRequest()

B) beginRequest()

C) start()

D) open()

22 / 30

22. What is the result of console.log(typeof NaN);?

A) "number"

B) "object"

C) "NaN"

D) "undefined"

23 / 30

23. Which method is used to test asynchronous code in Jest?

A) expectAsync()

B) testAsync()

C) wait()

D) done()

24 / 30

24. What is the main purpose of console.trace() in debugging?

A) To log all variables in scope.

B) To display the stack trace of a function call.

C) To stop code execution.

D) To measure execution time.

25 / 30

25. How can CSRF attacks be mitigated?

A) By validating user inputs.

B) By disabling cookies.

C) By using strong passwords.

D) By implementing CSRF tokens.

26 / 30

26. What is the purpose of the Coverage tab in Chrome DevTools?

A) To identify unused CSS and JavaScript.

B) To debug event listeners.

C) To display memory usage.

D) To measure network requests.

27 / 30

27. How does Object.entries() work in ES6?

A) Merges two objects

B) Converts an object into a string

C) Creates an object clone

D) Returns an array of key-value pairs from an object

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28. What does the document.querySelector() method do?

A) Selects all matching elements.

B) Creates a new DOM element.

C) Deletes an element from the DOM.

D) Selects the first matching element.

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29. Which of the following is a correct way to write JavaScript in an HTML document?

A) <script src="script.js"></script>

B) <javascript src="script.js"></javascript>

C) <script-link src="script.js"></script-link>

D) <script href="script.js"></script>

30 / 30

30. What is the purpose of the fetch() API?

A) To fetch cookies.

B) To fetch browser settings.

C) To make HTTP requests.

D) To fetch local files.

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