JavaScript MCQs with answers Page - 150

Here, you will find a collection of MCQ questions on JavaScript. Go through these questions to enhance your preparation for upcoming examinations and interviews.

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Q. How to convert a string to an integer in JavaScript?

  • (A) parseInt(str)
  • (B) Number(str)
  • (C) +str
  • (D) All of the above

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Q. Which statement is true for arrow functions?

  • (A) They bind their own 'this'
  • (B) They use lexical 'this'
  • (C) They are block-scoped
  • (D) They must use function keyword

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Q. What will be logged?

Code: 
let arr = [1, 2, 3];
arr.length = 1;
console.log(arr);
  • (A) [1]
  • (B) [1, 2, 3]
  • (C) []
  • (D) [1, 2]

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Q. What is the result of the following?

Code: 
console.log(typeof NaN);
  • (A) NaN
  • (B) number
  • (C) undefined
  • (D) object

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Q. What will this expression return?

Code: 
Boolean([]);
  • (A) true
  • (B) false
  • (C) undefined
  • (D) null

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Q. Which is not a valid JavaScript data type?

  • (A) Undefined
  • (B) Boolean
  • (C) Float
  • (D) Symbol

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Q. What is the output?

Code: 
console.log('2' + 2 - 2);
  • (A) 22
  • (B) 2
  • (C) NaN
  • (D) 0

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Q. What does the following return?

Code: 
[] == ![];
  • (A) true
  • (B) false
  • (C) undefined
  • (D) TypeError

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Q. Which method is used to convert an object to JSON string?

  • (A) JSON.parse()
  • (B) JSON.stringify()
  • (C) toString()
  • (D) parseJSON()

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Q. Which array method returns a new array with only truthy values?

  • (A) filter()
  • (B) map()
  • (C) reduce()
  • (D) forEach()

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