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Top 500 Javascript MCQ Interview Questions
Training
Top 500 Javascript MCQ Interview Questions
Question 351:
What is the output of console.log(!!'');?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 352:
Which of the following statements is used to create a function in JavaScript?
A) function myFunction() {}
B) def myFunction() {}
C) create myFunction() {}
D) func myFunction() {}
Answer:
A) function myFunction() {}
Question 353:
What does the Math.random() function return?
A) A random integer
B) A random decimal between 0 and 1
C) A random number between 1 and 10
D) None of the above
Answer:
B) A random decimal between 0 and 1
Question 354:
What will console.log('foo' === new String('foo')); output?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 355:
Which of the following is a valid way to create a promise in JavaScript?
A) new Promise()
B) Promise.resolve()
C) Promise.all()
D) All of the above
Answer:
D) All of the above
Question 356:
What is the output of console.log(5 + '5');?
A) 10
B) 55
C) undefined
D) error
Answer:
B) 55
Question 357:
Which method can be used to convert a string to a number?
A) Number()
B) parseFloat()
C) parseInt()
D) All of the above
Answer:
D) All of the above
Question 358:
What is the output of console.log(null === undefined);?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 359:
Which of the following is used to stop the execution of a function?
A) break
B) return
C) continue
D) stop
Answer:
B) return
Question 360:
What will console.log(typeof function(){}); output?
A) function
B) object
C) undefined
D) error
Answer:
A) function
Question 361:
Which of the following is not a valid way to check for equality?
A) ===
B) ==
C) !=
D) ==!
Answer:
D) ==!
Question 362:
What is the output of console.log([1, 2, 3].pop());?
A) 1
B) 3
C) undefined
D) error
Answer:
B) 3
Question 363:
Which method is used to join two or more arrays?
A) concat()
B) join()
C) merge()
D) combine()
Answer:
A) concat()
Question 364:
What is the output of console.log('1' + 2 + 3);?
A) 6
B) 123
C) 15
D) error
Answer:
B) 123
Question 365:
Which of the following is a correct way to write an anonymous function?
A) function() {}
B) let func = function() {}
C) const func = function() {}
D) All of the above
Answer:
D) All of the above
Question 366:
Which method can be used to find the index of an element in an array?
A) findIndex()
B) indexOf()
C) search()
D) Both A and B
Answer:
D) Both A and B
Question 367:
What will console.log(typeof {}); output?
A) object
B) array
C) function
D) undefined
Answer:
A) object
Question 368:
What is the output of console.log(1 + '1');?
A) 2
B) 11
C) '11'
D) error
Answer:
C) '11'
Question 369:
What is the output of console.log('hello'.charAt(0));?
A) h
B) hello
C) e
D) error
Answer:
A) h
Question 370:
Which of the following is the correct syntax for creating an object in JavaScript?
A) let obj = {};
B) let obj = new Object();
C) Both A and B
D) None of the above
Answer:
C) Both A and B
Question 371:
What will console.log([1, 2, 3].shift()); output?
A) 1
B) 3
C) undefined
D) error
Answer:
A) 1
Question 372:
Which method can be used to convert a string to lowercase?
A) toLowerCase()
B) lowerCase()
C) lowercase()
D) None of the above
Answer:
A) toLowerCase()
Question 373:
What is the output of console.log('10' - 1);?
A) 11
B) 9
C) '9'
D) error
Answer:
B) 9
Question 374:
Which operator is used to assign a value to a variable?
A) -
B) =
C) :
D) *
Answer:
B) =
Question 375:
What is the output of console.log([2] == [2]);?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 376:
Which of the following is a way to define a function in JavaScript?
A) function myFunction() {}
B) const myFunction = () => {};
C) Both A and B
D) None of the above
Answer:
C) Both A and B
Question 377:
What is the output of console.log(0 == '0');?
A) true
B) false
C) undefined
D) error
Answer:
A) true
Question 378:
Which of the following is the correct way to create an array in JavaScript?
A) let arr = [];
B) let arr = new Array();
C) Both A and B
D) None of the above
Answer:
C) Both A and B
Question 379:
What is the output of console.log([1, 2] == [1, 2]);?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 380:
What is the output of console.log('2' + 2);?
A) 4
B) '22'
C) 22
D) error
Answer:
B) '22'
Question 381:
What will console.log(typeof NaN); output?
A) number
B) NaN
C) undefined
D) error
Answer:
A) number
Question 382:
What is the output of console.log(true + false);?
A) true
B) false
C) 1
D) NaN
Answer:
C) 1
Question 383:
Which of the following is a falsy value in JavaScript?
A) 0
B) null
C) undefined
D) All of the above
Answer:
D) All of the above
Question 384:
What will console.log(2 === '2'); output?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 385:
Which of the following is the correct way to declare a variable in JavaScript?
A) var myVar;
B) let myVar;
C) const myVar;
D) All of the above
Answer:
D) All of the above
Question 386:
What is the output of console.log(typeof null);?
A) object
B) null
C) undefined
D) error
Answer:
A) object
Question 387:
What will console.log('5' + 5); output?
A) '55'
B) 10
C) '10'
D) error
Answer:
A) '55'
Question 388:
Which of the following is the result of console.log(typeof []);?
A) array
B) object
C) undefined
D) error
Answer:
B) object
Question 389:
What will console.log(5 + '5'); output?
A) 10
B) '55'
C) 5
D) error
Answer:
B) '55'
Question 390:
Which of the following is not a primitive data type in JavaScript?
A) String
B) Object
C) Number
D) Boolean
Answer:
B) Object
Question 391:
What will console.log([1, 2, 3].pop()); output?
A) 3
B) [1, 2]
C) 1
D) error
Answer:
A) 3
Question 392:
Which of the following is the correct way to concatenate two strings in JavaScript?
A) str1 + str2
B) str1.concat(str2)
C) Both A and B
D) None of the above
Answer:
C) Both A and B
Question 393:
What will console.log('Hello'.charAt(0)); output?
A) 'H'
B) 'Hello'
C) 'e'
D) error
Answer:
A) 'H'
Question 394:
What is the output of console.log(1 + '1');?
A) 2
B) '11'
C) '1'
D) error
Answer:
B) '11'
Question 395:
Which method is used to remove the last element from an array in JavaScript?
A) pop()
B) delete()
C) shift()
D) remove()
Answer:
A) pop()
Question 396:
What will console.log(typeof undefined); output?
A) undefined
B) object
C) function
D) error
Answer:
A) undefined
Question 397:
What will console.log('a' > 'A'); output?
A) true
B) false
C) NaN
D) error
Answer:
A) true
Question 398:
Which operator is used for strict equality in JavaScript?
A) =
B) ==
C) ===
D) !==
Answer:
C) ===
Question 399:
What is the output of console.log([1] == true);?
A) true
B) false
C) undefined
D) error
Answer:
A) true
Question 400:
Which of the following methods can be used to convert a string to a number in JavaScript?
A) parseInt()
B) Number()
C) parseFloat()
D) All of the above
Answer:
D) All of the above
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