Js Online Exam

Q1: Which symbol is used for single-line comments in JavaScript?

A) //
B) #
C) <!--
D) **

Q2: Which company developed JavaScript?

A) Netscape
B) Microsoft
C) Google
D) Sun Microsystems

Q3: Which of the following is a correct variable declaration?

A) var x = 10;
B) int x = 10;
C) let x == 10;
D) x := 10

Q4: Which keyword is used to declare a constant in JavaScript?

A) const
B) constant
C) final
D) let

Q5: How do you write 'Hello World' in an alert box?

A) msg('Hello World');
B) alertBox('Hello World');
C) alert('Hello World');
D) msgBox('Hello World');

Q6: What is the result of typeof null?

A) 'null'
B) 'object'
C) 'undefined'
D) 'number'

Q7: Which method adds a new element at the end of an array?

A) add()
B) push()
C) append()
D) insert()

Q8: What will `console.log(2 + '2')` output?

A) 4
B) 22
C) '4'
D) '2 + 2'

Q9: What does the `===` operator do?

A) Assigns value
B) Compares value and type
C) Compares reference only
D) Adds values

Q10: Which method converts JSON to a JavaScript object?

A) JSON.parse()
B) JSON.stringify()
C) JSON.toObject()
D) JSON.convert()

Q11: What is the default value of an uninitialized variable?

A) null
B) undefined
C) false
D) 0

Q12: Which object is the root of the DOM?

A) window
B) document
C) html
D) body

Q13: Which keyword is used to define a class in JavaScript?

A) class
B) define
C) object
D) constructor

Q14: Which loop will run at least once?

A) while
B) for
C) do-while
D) loop

Q15: Which function is used to delay execution?

A) pause()
B) timeout()
C) setTimeout()
D) sleep()

Q16: Which array method removes the first element?

A) pop()
B) shift()
C) splice()
D) unshift()

Q17: Which symbol is used for template literals?

A) `
B) '
C) "
D) ~

Q18: Which method joins array elements into a string?

A) merge()
B) join()
C) combine()
D) concat()

Q19: How do you define an arrow function?

A) () => {}
B) function => {}
C) => () {}
D) () -> {}

Q20: What is the output of `typeof NaN`?

A) 'NaN'
B) 'undefined'
C) 'number'
D) 'object'

Q21: Which function is used to round a number down?

A) Math.round()
B) Math.ceil()
C) Math.floor()
D) Math.trunc()

Q22: Which operator is used for logical AND?

A) &&
B) &
C) and
D) &&&

Q23: How do you check if 'x' is not equal to 'y'?

A) x != y
B) x !== y
C) x <> y
D) Both 1 and 2

Q24: How do you get the length of an array?

A) array.size()
B) array.length
C) length(array)
D) array.count()

Q25: What will `typeof undefined` return?

A) 'null'
B) 'undefined'
C) 'object'
D) 'error'

Q26: What is the result of `0 == '0'`?

A) false
B) true
C) NaN
D) undefined

Q27: Which keyword is used to define a block-scoped variable?

A) var
B) const
C) let
D) define

Q28: Which event occurs when the user clicks on an HTML element?

A) onclick
B) onhover
C) onchange
D) onpress

Q29: Which of the following is not a primitive data type?

A) string
B) number
C) boolean
D) object

Q30: What will `Boolean('')` return?

A) true
B) false
C) undefined
D) null

Q31: How do you create an object?

A) {}
B) []
C) <>
D) ()

Q32: Which method can be used to remove elements from an array?

A) slice()
B) splice()
C) cut()
D) delete()

Q33: What does DOM stand for?

A) Document Object Model
B) Data Object Model
C) Document Oriented Module
D) Digital Object Mapper

Q34: What is the correct syntax for an if statement?

A) if x = 5 then
B) if (x == 5)
C) if x == 5 {}
D) if x = 5

Q35: Which object is used for mathematical functions?

A) calc
B) math
C) Math
D) Calculate

Q36: How do you stop a setInterval() timer?

A) stop()
B) pause()
C) clearInterval()
D) cancel()

Q37: What is a callback function?

A) A function passed to another function
B) A function that returns a string
C) A loop function
D) A function called recursively

Q38: What is hoisting?

A) Moving functions to end
B) Variable declaration moved to top
C) Loop optimization
D) Event bubbling

Q39: What is `this` keyword used for?

A) Refers to global scope
B) Refers to current object
C) Refers to window only
D) None of the above

Q40: Which operator is used to spread array elements?

A) ...
B) ++
C) **
D) ===

Q41: Which method converts a value to a string?

A) String(value)
B) toString()
C) value.toString()
D) All of the above

Q42: How do you check the type of a variable?

A) type()
B) typeof
C) instanceof
D) typeof()

Q43: Which function merges arrays?

A) combine()
B) merge()
C) concat()
D) join()

Q44: What will `Array.isArray([])` return?

A) false
B) true
C) null
D) error

Q45: What does `JSON.stringify()` do?

A) Parses JSON
B) Converts JS to JSON string
C) Compresses JSON
D) Encrypts JSON

Q46: Which method is used to find an element in an array?

A) search()
B) find()
C) locate()
D) match()

Q47: How can you write a function in JavaScript?

A) function myFunc()
B) def myFunc()
C) func myFunc()
D) new function()

Q48: Which loop is best for arrays?

A) for
B) forEach
C) while
D) do-while

Q49: Which method is used to add an element at the end of an array in JavaScript?

A) append()
B) add()
C) push()
D) insert()

Q50: What will be the result of `[] + []` in JavaScript?

A) An error
B) '[object Object][object Object]'
C) '' (empty string)
D) 'undefinedundefined'