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Top 500 Javascript MCQ Interview Questions
Training
Top Javascript CSS MCQ Interview Questions
Question 101:
Which of the following is a primitive data type in JavaScript?
A) Array
B) Object
C) String
D) Function
Answer:
C) String
Question 102:
What will console.log(1 == '1'); output?
A) true
B) false
C) undefined
D) error
Answer:
A) true
Question 103:
Which method is used to add one or more elements to the end of an array?
A) push()
B) pop()
C) shift()
D) unshift()
Answer:
A) push()
Question 104:
What will console.log('10' + 1); output?
A) 11
B) 101
C) error
D) undefined
Answer:
B) 101
Question 105:
Which of the following is used to declare a variable in JavaScript?
A) var
B) let
C) const
D) All of the above
Answer:
D) All of the above
Question 106:
What is the output of console.log(typeof null);?
A) null
B) object
C) undefined
D) error
Answer:
B) object
Question 107:
Which of the following is a method to convert a string to a number?
A) parseInt()
B) parseFloat()
C) Number()
D) All of the above
Answer:
D) All of the above
Question 108:
What does the Array.isArray() method do?
A) Checks if a variable is an array
B) Creates a new array
C) Returns the length of an array
D) None of the above
Answer:
A) Checks if a variable is an array
Question 109:
Which of the following is not a falsy value in JavaScript?
A) 0
B) ""
C) false
D) 1
Answer:
D) 1
Question 110:
What will be the output of console.log(5 === '5');?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 111:
Which of the following methods removes the last element from an array?
A) pop()
B) shift()
C) splice()
D) slice()
Answer:
A) pop()
Question 112:
What will console.log([1, 2, 3].includes(2)); output?
A) true
B) false
C) undefined
D) error
Answer:
A) true
Question 113:
What is the output of console.log(Math.max(1, 2, 3));?
A) 1
B) 2
C) 3
D) undefined
Answer:
C) 3
Question 114:
Which keyword is used to create a new function in JavaScript?
A) function
B) method
C) create
D) new
Answer:
A) function
Question 115:
What does console.log(3 + 2 + '7'); output?
A) 12
B) 57
C) 27
D) error
Answer:
B) 57
Question 116:
Which method is used to remove the first element from an array?
A) pop()
B) shift()
C) slice()
D) splice()
Answer:
B) shift()
Question 117:
What is the output of console.log(!!null);?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 118:
Which method can be used to iterate over an array?
A) map()
B) forEach()
C) filter()
D) All of the above
Answer:
D) All of the above
Question 119:
What will console.log('Hello'.substring(1, 4)); output?
A) Hel
B) ell
C) llo
D) Hello
Answer:
B) ell
Question 120:
Which operator is used for strict equality comparison?
A) ==
B) ===
C) !=
D) !==
Answer:
B) ===
Question 121:
What does the map() method do?
A) Transforms each element of an array
B) Filters elements based on a condition
C) Sorts an array
D) None of the above
Answer:
A) Transforms each element of an array
Question 122:
What is the output of console.log(1 + 2 + '3' - 1);?
A) 3
B) 23
C) 2
D) error
Answer:
A) 2
Question 123:
Which of the following is a way to create an object in JavaScript?
A) let obj = {};
B) let obj = new Object();
C) let obj = Object.create(null);
D) All of the above
Answer:
D) All of the above
Question 124:
What is the output of console.log('5' - 2);?
A) 3
B) 5
C) undefined
D) error
Answer:
A) 3
Question 125:
Which of the following will trigger a TypeError in JavaScript?
A) null.length
B) undefined.length
C) 1.length
D) All of the above
Answer:
D) All of the above
Question 126:
What is the output of console.log([2] == [2]);?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 127:
What is the output of console.log('abc'.charAt(1));?
A) a
B) b
C) c
D) undefined
Answer:
B) b
Question 128:
What does the JSON.stringify() method do?
A) Converts a JavaScript object to a JSON string
B) Parses a JSON string into a JavaScript object
C) Validates a JSON string
D) None of the above
Answer:
A) Converts a JavaScript object to a JSON string
Question 129:
Which method is used to add an element to the end of an array?
A) push()
B) unshift()
C) pop()
D) shift()
Answer:
A) push()
Question 130:
What is the output of console.log(!!undefined);?
A) true
B) false
C) null
D) error
Answer:
B) false
Question 131:
Which method is used to convert a JSON string into a JavaScript object?
A) JSON.parse()
B) JSON.stringify()
C) JSON.convert()
D) JSON.toObject()
Answer:
A) JSON.parse()
Question 132:
What is the output of console.log('1' + 1);?
A) 2
B) 11
C) '1'
D) error
Answer:
B) 11
Question 133:
Which keyword is used to declare a variable in JavaScript?
A) var
B) let
C) const
D) All of the above
Answer:
D) All of the above
Question 134:
What does the 'this' keyword refer to in JavaScript?
A) The global object
B) The current function context
C) The current class instance
D) None of the above
Answer:
B) The current function context
Question 135:
Which of the following is a falsy value in JavaScript?
A) 0
B) "" (empty string)
C) null
D) All of the above
Answer:
D) All of the above
Question 136:
What is the output of console.log(typeof NaN);?
A) number
B) undefined
C) object
D) error
Answer:
A) number
Question 137:
Which of the following is used to handle exceptions in JavaScript?
A) try...catch
B) throw
C) finally
D) All of the above
Answer:
D) All of the above
Question 138:
What is the output of console.log('2' + '2');?
A) 4
B) 22
C) '22'
D) error
Answer:
B) 22
Question 139:
Which function is used to remove the last element from an array?
A) pop()
B) push()
C) shift()
D) unshift()
Answer:
A) pop()
Question 140:
What does the '===' operator do in JavaScript?
A) Compares two values for equality
B) Compares two values and types for equality
C) Compares two values for inequality
D) None of the above
Answer:
B) Compares two values and types for equality
Question 141:
What is the output of console.log(1 == '1');?
A) true
B) false
C) undefined
D) error
Answer:
A) true
Question 142:
What is the output of console.log(typeof null);?
A) object
B) null
C) undefined
D) error
Answer:
A) object
Question 143:
Which of the following methods is used to convert a string to an integer?
A) parseInt()
B) parseFloat()
C) Number()
D) All of the above
Answer:
D) All of the above
Question 144:
What is the output of console.log('3' - 2);?
A) 1
B) '1'
C) NaN
D) error
Answer:
A) 1
Question 145:
Which method is used to remove the first element from an array?
A) shift()
B) pop()
C) unshift()
D) push()
Answer:
A) shift()
Question 146:
What is the output of console.log(1 === '1');?
A) true
B) false
C) undefined
D) error
Answer:
B) false
Question 147:
Which method is used to add one or more elements to the beginning of an array?
A) push()
B) pop()
C) unshift()
D) shift()
Answer:
C) unshift()
Question 148:
What is the output of console.log(2 + '2');?
A) 4
B) '22'
C) 22
D) error
Answer:
B) '22'
Question 149:
Which of the following is used to define a block scope variable in JavaScript?
A) var
B) let
C) const
D) All of the above
Answer:
D) All of the above
Question 150:
What is the output of console.log(!!'');?
A) true
B) false
C) null
D) error
Answer:
B) false
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