js-quiz-03

Js Quiz 03

Improve your JS skills with our interactive quizzes. Choose a quiz below and test your knowledge!

You have 10 minutes to complete 25 questions.

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10:00

01. Which of the following is used to declare variables in JavaScript?

var

let

const

All of the above

Explanation: JavaScript allows you to declare variables using var, let, or const.

02. What will console.log(typeof Infinity) return?

"null"

"number"

"undefined"

"string"

Explanation: In JavaScript, Infinity is a special numeric value representing a number that exceeds the upper limit of what can be represented. The typeof operator considers it as a "number".

03. How do you write an "if" statement in JavaScript?

if i == 5 then

if i == 5:

if i = 5

if (i == 5)

Explanation: Correct syntax for an if statement in JavaScript is if (condition). Ex: if (5 > 3) { console.log("5 is greater than 3"); }

04. Which array method checks if at least one element passes a test?

every()

filter()

some()

find()

Explanation: some() returns true if any array element passes the given condition.

05. Which is the correct syntax for a for loop?

for (i <= 5; i++)

for (i = 0; i <= 5; i++)

for (i++)

for i = 1 to 5

Explanation: A valid for loop in JavaScript requires initialization, condition, and increment.
Ex : for (let i = 0; i < 5; i++) { console.log(i); }

06. What does parseFloat('10.5abc') return?

10.5

NaN

undefined

null

Explanation: parseFloat() extracts and converts the valid numeric part of the string.

07. Which operator is used for exponentiation in JavaScript?

^

**

%%

^^

Explanation: ** is the exponentiation operator introduced in ES6.

08. What is the default return value of a function in JavaScript?

null

0

undefined

NaN

Explanation: A function without an explicit return statement returns undefined.

09. Which function is used to delay execution of code in JavaScript?

setInterval()

clearTimeout()

clearInterval()

setTimeout()

Explanation: setTimeout() delays code execution by a specified number of milliseconds.

10. What will console.log("5" - 2) return?

3

"52"

"5-2"

NaN

Explanation: The - operator coerces the string "5" to a number.

11. Which statement stops the execution of a loop?

stop

break

exit

terminate

Explanation: The break statement immediately exits the current loop.

12. How do you remove duplicates from an array?

new Set([...array])

array.unique()

array.filter()

array.reduce()

Explanation: A Set automatically removes duplicates, and spreading it back into an array maintains array format.

13. What will console.log(!!false) output?

NaN

true

undefined

false

Explanation: !! coerces a value to a boolean. false remains false.

14. What does this refer to in the global scope?

window object

document object

global object

undefined

Explanation: In the global scope, this refers to the window object in browsers.

15. What is the output of typeof NaN?

object

NaN

undefined

number

Explanation: NaN is a special number value.

16. What will console.log([10] + [20]) output?

30

[10, 20]

"1020"

NaN

Explanation: Arrays are converted to strings during concatenation.

17. How do you define default values for function parameters?

function foo(a = 10)

function foo(a || 10)

function foo(a: 10)

function foo(a -> 10)

Explanation: Default parameter syntax was introduced in ES6.

18. What is the purpose of the bind() method?

To return a bound object

To execute a function immediately

To permanently set this context

To inherit from another class

Explanation: bind() creates a new function with the provided this value.

19. Which of the following will throw an error?

let x;

const x;

var x;

x = 10;

Explanation: Constants must be initialized when declared.

20. What is the difference between slice() and splice()?

slice() modifies the array, splice() does not

Both modify the array

Both do not modify the array

splice() modifies the array, slice() does not

Explanation: splice() changes the original array, while slice() creates a shallow copy.

21. What does Promise.all() do?

Executes promises sequentially

Resolves when all promises resolve

Resolves when the first promise resolves

Returns the first rejected promise

Explanation: Promise.all() resolves only when all promises have resolved.

22. How do you handle exceptions in JavaScript?

try-catch block

catch-try block

throw block

finally block

Explanation: Errors are caught using the try-catch structure.

23. What will console.log([..."hello"]) output?

["hello"]

["h", "e", "l", "l", "o"]

["h", "ello"]

Error

Explanation: The spread operator splits strings into individual characters.

24. What is the use of the finally block?

Runs code only if no errors

Runs code only if there are errors

Runs code after try or catch blocks

Skips execution if no errors occur

Explanation: The finally block always executes after try or catch.

25. Which of the following is a valid WeakSet method?

add()

keys()

forEach()

map()

Explanation: WeakSet only has add(), delete(), and has() methods.

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