JavaScript Exam 1

1. What keyword creates a changeable variable?

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

2. What is the boolean value of the string “0”?

Boolean("0")

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

3. What is the length of this array?

let arr = ["x", "y", "z"];

A) 1
B) 2
C) 3
D) 4

4. What does a function return if it has no return statement?

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

5. Can JavaScript be included in any valid HTML file?

A) Yes
B) No
C) Only in <head>
D) Only as external file

6. What will this display?

let x = 4; let y = 6; let z = x + "" + y; alert(z);

A) 10
B) “10”
C) 46
D) “46”

7. Will this behave the same in all browsers?

"hello".substring(-1);

A) Yes
B) No
C) Only modern browsers
D) Only Chrome

8. What does parseInt return here?

parseInt(52.9);

A) 52
B) 53
C) 52.9
D) NaN

9. Can browser JavaScript directly read/write arbitrary local files?

A) Yes
B) Only with user permission
C) No
D) Only in special builds

10. What will this loop alert?

let total=0; for(let i=1;i<=8;i++){ if(i%3===0) continue; if(i>5) break; total+=i } alert(total);

A) 6
B) 9
C) 12
D) 15

12. Do all JavaScript engines behave identically for every feature?

A) Yes
B) No
C) Only ES6 features do
D) Only in strict mode

13. What is the result of “super”+”man”?

A) super man
B) man super
C) superman
D) “super”+”man”

14. What does s.replace(/l/g,”#”) do to “balloon”?

A) Replaces first ‘l’
B) Replaces all ‘l’s
C) No change
D) Throws error

15. What does s.replace(“l”,”#”) do to “balloon”?

A) All ‘l’s replaced
B) Only first ‘l’ replaced
C) No change
D) Error

16. Which returns the integer part of a number?

Math.floor(3.9)

A) 3
B) 4
C) 3.9
D) NaN

17. What will this alert?

let a=4, b=2; function calc(x){ b = a + x; return ++b; } alert(calc(3));

A) 6
B) 7
C) 8
D) 9

18. How to append 5 to array nums?

A) nums.add(5)
B) nums.unshift(5)
C) nums.push(5)
D) nums.insert(5)

19. Which event fires when the mouse enters an element?

A) onmouseout
B) onmouseenter
C) onmouseover
D) onleave

20. typeof Infinity returns?

A) “undefined”
B) “object”
C) “number”
D) “Infinity”

21. Which keyword declares a constant?

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

22. What does Number(“123”) return?

A) “123”
B) 123
C) NaN
D) undefined

23. What does console.log(“5” – 2) output?

A) “52”
B) 52
C) 3
D) NaN

24. What is the result of [] + [] ?

A) 0
B) “” (empty string)
C) []
D) undefined

25. typeof [] returns?

A) “array”
B) “object”
C) “list”
D) “collection”

26. Which method removes the last item of an array?

A) shift()
B) pop()
C) remove()
D) delete()

27. What value does let x; create?

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

28. What does “hello”.toUpperCase() return?

A) hello
B) HELLO
C) Hello
D) error

29. Which operator checks both value and type?

A) ==
B) =
C) ===
D) =>

30. What does “cat”.includes(“a”) return?

A) “a”
B) false
C) true
D) error

31. What does typeof null return?

A) “null”
B) “object”
C) “undefined”
D) “none”

32. What does !true evaluate to?

A) true
B) false
C) undefined
D) 1

33. Which literal creates an array?

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

34. What does push() return?

A) New array
B) Removed value
C) New length (number)
D) Nothing

35. Which loop runs the body at least once?

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

36. Which event triggers on a click?

A) onHover
B) onClick
C) onMouseOut
D) onEnter

37. What is the result of NaN === NaN ?

A) true
B) false
C) undefined
D) throws error

38. Which is a primitive type?

A) Array
B) Object
C) String
D) Function

39. typeof function(){} returns?

A) “object”
B) “function”
C) “method”
D) “undefined”

40. What does JSON.stringify({a:1}) do?

A) Parse JSON to object
B) Convert object to JSON string
C) Minify code
D) Encrypt object

41. Which method adds elements to the start of an array?

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

42. What does “10” + 1 produce?

A) 11
B) “11”
C) “101”
D) NaN

43. How to make a shallow copy of array a?

A) let b = a;
B) let b = a.slice()
C) let b = a.pop()
D) let b = a.join()

44. Which checks array membership?

A) arr.indexOf(x) !== -1
B) arr.contains(x)
C) x in arr
D) arr.has(x)

45. typeof (function(){}) returns?

A) “object”
B) “function”
C) “undefined”
D) “method”

46. Which method converts a string to lowercase?

A) toLowerCase()
B) tolower()
C) lower()
D) downcase()

47. What does 0 == “0” evaluate to?

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

48. Which declares a block-scoped variable?

A) var x = 1;
B) let x = 1;
C) function x() {}
D) const x = 1;

49. Which method splits a string into an array?

A) join()
B) split()
C) slice()
D) toArray()

50. Which array method returns true if every element passes the test?

A) some()
B) every()
C) filter()
D) map()

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