JavaScript MCQs with answers Page - 145

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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A

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Q. How do you write a conditional statement for executing code if 'x' is greater than 5?

  • (A) if x > 5
  • (B) if (x > 5)
  • (C) if x > 5 then
  • (D) if (x > 5) then

A

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Q. What will be logged?

Code: 
let a = 1;
let b = a++;
console.log(b);
  • (A) 2
  • (B) 1
  • (C) undefined
  • (D) NaN

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Q. Which object method returns an array of a given object's property names?

  • (A) Object.keys()
  • (B) Object.names()
  • (C) Object.get()
  • (D) Object.entries()

A

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Q. What will be the result?

Code: 
typeof function(){};
  • (A) function
  • (B) object
  • (C) undefined
  • (D) function()

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Q. Which operator is used to merge two arrays?

  • (A) +
  • (B) &
  • (C) concat()
  • (D) merge()

A

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Q. What will this return?

Code: 
[1, 2, 3].includes(2);
  • (A) true
  • (B) false
  • (C) undefined
  • (D) NaN

A

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Q. Which of the following is a falsy value?

  • (A) 0
  • (B) null
  • (C) undefined
  • (D) All of the above

A

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Q. What is the value of x?

Code: 
let x = '5';
x = +x;
  • (A) '5'
  • (B) 5
  • (C) NaN
  • (D) undefined

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Q. What does this expression return?

Code: 
Boolean('false');
  • (A) false
  • (B) true
  • (C) undefined
  • (D) Error

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Q. What is a Promise in JavaScript?

  • (A) A function that never runs
  • (B) A placeholder for a future value
  • (C) A data type
  • (D) An error object

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