Top 500 Javascript MCQ Interview questions | Career in IT

Question 1: Which of the following is the correct syntax to declare a JavaScript variable?

Answer: A) var variableName;

Question 2: What is the output of the following code: console.log(typeof null);?

Answer: B) object

Question 3: Which of the following is not a JavaScript data type?

Answer: D) Character

Question 4: Which of the following methods can be used to convert a string to a number in JavaScript?

Answer: A) parseInt(), D) Number()

Question 5: What is the correct way to create a function in JavaScript?

Answer: B) function myFunction() { }

Question 6: What will be the output of console.log(0.1 + 0.2 === 0.3);?

Answer: B) false

Question 7: Which of the following keywords is used to define a constant in JavaScript?

Answer: A) const

Question 8: What is the purpose of the this keyword in JavaScript?

Answer: C) Refers to the object that is executing the current function

Question 9: Which method is used to remove the last element from an array in JavaScript?

Answer: A) pop()

Question 10: Which of the following is an example of a first-class function?

Answer: D) All of the above

Question 11: How can you create an object in JavaScript?

Answer: D) All of the above

Question 12: What is the output of console.log(typeof NaN);?

Answer: A) Number

Question 13: Which of the following statements is used to create a conditional statement in JavaScript?

Answer: D) Both A and B

Question 14: What does the Math.random() function return?

Answer: B) A random floating-point number between 0 and 1

Question 15: Which operator is used to assign a value to a variable in JavaScript?

Answer: B) =

Question 16: What is the purpose of the JSON.stringify() method?

Answer: A) Converts a JSON object into a string

Question 17: How do you declare a JavaScript array?

Answer: A) var arr = []; , D) var arr = new Array();

Question 18: Which of the following is a JavaScript framework?

Answer: D) All of the above

Question 19: What will console.log(2 + '2'); output?

Answer: B) 22

Question 20: What is the purpose of the setTimeout() function in JavaScript?

Answer: A) To create a delay in the execution of a function

Question 21: Which of the following is a way to handle exceptions in JavaScript?

Answer: D) Both A and C

Question 22: What is the output of console.log('Hello' + 5 + 10);?

Answer: A) Hello510

Question 23: Which built-in method combines two or more arrays in JavaScript?

Answer: A) concat()

Question 24: What is the purpose of the localStorage object?

Answer: B) To store data permanently in the user's browser

Question 25: How do you declare a variable in JavaScript?

Answer: D) All of the above

Question 26: What will console.log(!!null); output?

Answer: B) false

Question 27: Which of the following methods can be used to iterate over an array?

Answer: D) All of the above

Question 28: How can you add a comment in JavaScript?

Answer: D) Both A and B

Question 29: Which method is used to access the first element of an array?

Answer: C) array[0]

Question 30: What will console.log(1 == '1'); output?

Answer: A) true

Question 31: Which of the following is a valid way to declare an object?

Answer: D) Both A and B

Question 32: What does the slice() method do in JavaScript?

Answer: C) Returns a shallow copy of a portion of an array

Question 33: Which of the following functions can be used to read user input in JavaScript?

Answer: A) prompt()

Question 34: What is the output of console.log([1] == true);?

Answer: A) true

Question 35: Which method is used to find the index of an element in an array?

Answer: D) Both A and B

Question 36: Which operator is used to compare both value and type in JavaScript?

Answer: B) ===

Question 37: What is the purpose of the typeof operator?

Answer: A) To determine the type of a variable

Question 38: How can you check if a variable is an array in JavaScript?

Answer: D) Both A and B

Question 39: Which function is used to parse a JSON string into a JavaScript object?

Answer: B) JSON.parse()

Question 40: Which of the following is a truthy value in JavaScript?

Answer: D) 1

Question 41: What will be the output of console.log(typeof []);?

Answer: B) object

Question 42: How can you create a copy of an array in JavaScript?

Answer: D) All of the above

Question 43: Which of the following can be used to trigger a function in JavaScript?

Answer: D) All of the above

Question 44: What is a closure in JavaScript?

Answer: A) A function with access to its own scope, the outer function's scope, and the global scope

Question 45: What is event delegation in JavaScript?

Answer: A) Attaching an event handler to a parent element

Question 46: What is the purpose of the 'this' keyword in JavaScript?

Answer: D) Both B and C

Question 47: How can you prevent an event from bubbling up in JavaScript?

Answer: D) Both A and C

Question 48: What is the purpose of the fetch() function in JavaScript?

Answer: D) All of the above

Question 49: Which of the following is a way to define a function in JavaScript?

Answer: D) All of the above

Question 50: What is a promise in JavaScript?

Answer: A) A way to handle asynchronous operations

Showing 1-50 of 500 questions

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1. B) JSON.parse()
2. A) number
3. A) number
4. A) number
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10. A) number
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29. A) number
2. A) number
2. A) number
2. A) number
2. A) number
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2. A) number
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2. A) number
2. A) number
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2. A) number
2. A) number
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2. A) number
2. A) number

500 Javascript MCQ Interview Questions

Answer Key

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