JavaScript MCQ:-
- What does JavaScript use to indicate the start and end of a block of code?
- A) Curly braces
{ } - B) Parentheses
( ) - C) Square brackets
[ ] - D) Angle brackets
< >
- A) Curly braces
- Which of the following is the correct syntax to create a function in JavaScript?
- A)
function myFunction[] {} - B)
function myFunction() {} - C)
function myFunction() () {} - D)
function myFunction{ }
- A)
- How do you declare a variable in JavaScript?
- A)
var variableName; - B)
variableName = var; - C)
variableName: var; - D)
declare variableName;
- A)
- Which operator is used to assign a value to a variable in JavaScript?
- A)
== - B)
!= - C)
= - D)
===
- A)
- How do you write a single-line comment in JavaScript?
- A)
/* This is a comment */ - B)
<!-- This is a comment --> - C)
// This is a comment - D)
-- This is a comment
- A)
- Which of the following is not a valid JavaScript data type?
- A)
String - B)
Number - C)
Boolean - D)
Character
- A)
- What will the following code output:
console.log(typeof 'Hello');?- A)
string - B)
String - C)
text - D)
char
- A)
- Which method is used to remove whitespace from both ends of a string?
- A)
trim() - B)
strip() - C)
remove() - D)
cut()
- A)
- How can you convert a string to an integer in JavaScript?
- A)
parseInt() - B)
parseString() - C)
toInteger() - D)
convert()
- A)
- What does the
push()method do in JavaScript arrays?- A) Removes the last element
- B) Adds an element to the end
- C) Adds an element to the beginning
- D) Removes the first element
- Which keyword is used to create a new object in JavaScript?
- A)
object - B)
new - C)
create - D)
this
- A)
- How do you check if two values are equal in JavaScript, considering type?
- A)
== - B)
=== - C)
!= - D)
!==
- A)
- Which function is used to parse a JSON string into an object in JavaScript?
- A)
JSON.parse() - B)
JSON.stringify() - C)
parseJSON() - D)
stringifyJSON()
- A)
- What will
console.log(0.1 + 0.2 === 0.3);output?- A)
true - B)
false - C)
undefined - D)
NaN
- A)
- How can you access the first element of an array named
arr?- A)
arr[0] - B)
arr.first() - C)
arr.begin() - D)
arr.get(1)
- A)
- Which statement is used to exit a loop in JavaScript?
- A)
stop - B)
exit - C)
break - D)
continue
- A)
- What will the following code output:
console.log(1 + '1');?- A)
2 - B)
11 - C)
NaN - D)
undefined
- A)
- How do you define a constant in JavaScript?
- A)
const variableName; - B)
constant variableName; - C)
let variableName; - D)
const variableName = value;
- A)
- Which method is used to find the length of an array in JavaScript?
- A)
length() - B)
size() - C)
count() - D)
length
- A)
- What does the
returnstatement do in a function?- A) Exits the function
- B) Returns a value from the function
- C) Ends the loop
- D) Terminates the program
- How can you check if a variable
xis an instance of a particular objectY?- A)
x.instanceof(Y) - B)
x.isInstance(Y) - C)
x instanceof Y - D)
instanceof(x, Y)
- A)
- What is the default value of an uninitialized variable in JavaScript?
- A)
0 - B)
null - C)
undefined - D)
NaN
- A)
- How do you create an empty object in JavaScript?
- A)
var obj = {}; - B)
var obj = []; - C)
var obj = (); - D)
var obj = new Object();
- A)
- Which method is used to add an item to the beginning of an array?
- A)
push() - B)
pop() - C)
shift() - D)
unshift()
- A)
- How do you create a new array with elements added to an existing array?
- A)
arr.concat(newElements) - B)
arr.add(newElements) - C)
arr.merge(newElements) - D)
arr.append(newElements)
- A)
- Which keyword is used to define a block scope variable in JavaScript?
- A)
var - B)
let - C)
const - D)
block
- A)
- What is the result of
Boolean(0)in JavaScript?- A)
true - B)
false - C)
undefined - D)
null
- A)
- Which method converts an object to a JSON string?
- A)
JSON.parse() - B)
JSON.stringify() - C)
toJSON() - D)
convertToJSON()
- A)
- How do you execute a function every 5 seconds?
- A)
setTimeout(myFunction, 5000); - B)
setInterval(myFunction, 5000); - C)
setDelay(myFunction, 5000); - D)
setExecute(myFunction, 5000);
- A)
- Which function is used to evaluate an expression in JavaScript?
- A)
eval() - B)
calculate() - C)
compute() - D)
evaluate()
- A)
- What does the
thiskeyword refer to in JavaScript?- A) The global object
- B) The object that is currently executing the code
- C) The function that is currently executing
- D) The window object
- How do you check if a number is NaN?
- A)
isNaN() - B)
checkNaN() - C)
isNotNumber() - D)
NaN()
- A)
- Which property of the
windowobject provides information about the browser’s user agent?- A)
window.location - B)
window.navigator - C)
window.screen - D)
window.document
- A)
- What does
JSON.stringify()do?- A) Converts a JavaScript object into a JSON string
- B) Parses a JSON string into a JavaScript object
- C) Evaluates a JSON string
- D) Formats a JSON string
- Which of the following will correctly check if a variable is an array?
- A)
Array.isArray(variable) - B)
variable.isArray() - C)
typeof variable === 'array' - D)
variable instanceof Array
- A)
- What is the result of
3 + '3'in JavaScript?- A)
6 - B)
33 - C)
NaN - D)
undefined
- A)
- Which statement will output the largest number in an array
arr?- A)
Math.max(arr) - B)
arr.max() - C)
Math.max(...arr) - D)
arr.reduce(max)
- A)
- How can you stop a loop from executing further in JavaScript?
- A)
stop - B)
halt - C)
break - D)
return
- A)
- Which method will remove the last item from an array?
- A)
pop() - B)
shift() - C)
push() - D)
unshift()
- A)
- How do you access a property of an object in JavaScript?
- A)
object.property - B)
object->property - C)
object[property] - D)
object.property()
- A)
- What will
console.log([1] == [1]);output?- A)
true - B)
false - C)
undefined - D)
NaN
- A)
- Which operator is used to check for inequality?
- A)
!= - B)
!== - C)
<> - D)
!=!
- A)
- How do you define a class in JavaScript?
- A)
class MyClass {} - B)
define MyClass {} - C)
function MyClass() {} - D)
new class MyClass {}
- A)
- Which keyword is used to handle errors in JavaScript?
- A)
error - B)
catch - C)
try - D)
throw
- A)
- What is the result of
10 % 3in JavaScript?- A)
3 - B)
1 - C)
10 - D)
0
- A)
- How do you create a new instance of a class in JavaScript?
- A)
new ClassName() - B)
ClassName.new() - C)
ClassName.create() - D)
ClassName()
- A)
- Which function is used to read a value from a text input field?
- A)
getValue() - B)
readValue() - C)
value() - D)
input.value
- A)
- How do you compare two objects in JavaScript?
- A)
== - B)
=== - C)
JSON.stringify() - D)
Object.equals()
- A)
- What is the result of
null == undefined?- A)
true - B)
false - C)
undefined - D)
NaN
- A)
- How do you define a method within an object?
- A)
object.method = function() {} - B)
object.method = () => {} - C)
object.method() {} - D)
object.method() = function() {}
- A)
- Which method adds one or more elements to the end of an array and returns the new length of the array?
- A)
push() - B)
pop() - C)
shift() - D)
unshift()
- A)
- What will
console.log('5' - 2);output?- A)
3 - B)
52 - C)
NaN - D)
undefined
- A)
- How do you check if a string contains a certain substring?
- A)
str.includes(substring) - B)
str.has(substring) - C)
str.contains(substring) - D)
str.indexOf(substring)
- A)
- Which method is used to join all elements of an array into a string?
- A)
join() - B)
combine() - C)
concat() - D)
merge()
- A)
- How do you create a promise in JavaScript?
- A)
new Promise() - B)
Promise.create() - C)
Promise.new() - D)
new Promise(function(resolve, reject) {})
- A)
- What will
console.log(1 < 2 < 3);output?- A)
true - B)
false - C)
undefined - D)
NaN
- A)
- How do you call a function that is stored in a variable?
- A)
variable() - B)
call(variable) - C)
variable.call() - D)
variable.invoke()
- A)
- Which method removes whitespace from the start of a string?
- A)
trimStart() - B)
trimLeft() - C)
stripStart() - D)
removeWhitespace()
- A)
- How do you set a timeout to execute a function after 2 seconds?
- A)
setTimeout(function, 2000) - B)
delay(function, 2000) - C)
setInterval(function, 2000) - D)
schedule(function, 2000)
- A)
- Which of the following is used to create a new array in JavaScript?
- A)
Array.create() - B)
new Array() - C)
Array.new() - D)
Array.build()
- A)
- How do you remove an element from a specific index in an array?
- A)
splice(index, 1) - B)
remove(index) - C)
delete(index) - D)
slice(index, 1)
- A)
- Which method returns the index of the first occurrence of a specified value in a string?
- A)
indexOf() - B)
find() - C)
search() - D)
positionOf()
- A)
- How do you get a substring from a string?
- A)
substring(start, end) - B)
slice(start, end) - C)
substr(start, length) - D) All of the above
- A)
- What will
console.log('hello'.toUpperCase());output?- A)
HELLO - B)
hello - C)
Hello - D)
HELLO
- A)
- How do you define a default parameter value in a function?
- A)
function myFunction(param = defaultValue) {} - B)
function myFunction(param, defaultValue) {} - C)
function myFunction(param, defaultValue = param) {} - D)
function myFunction(param: defaultValue) {}
- A)
- What will
console.log(2 + '2' - 1);output?- A)
21 - B)
22 - C)
20 - D)
1
- A)
- Which method is used to sort the elements of an array?
- A)
sort() - B)
order() - C)
arrange() - D)
sequence()
- A)
- How do you create a new RegExp object?
- A)
new RegExp(pattern) - B)
RegExp.create(pattern) - C)
RegExp(pattern) - D)
new RegExp(pattern, flags)
- A)
- Which keyword is used to define a class method in JavaScript?
- A)
class - B)
method - C)
function - D)
static
- A)
- How do you determine if an object is a function?
- A)
typeof object === 'function' - B)
object.isFunction() - C)
object instanceof Function - D)
object.type()
- A)
- What does the
filter()method do in JavaScript arrays?- A) Returns a new array with elements that pass a test
- B) Sorts the array elements
- C) Finds the first element that passes a test
- D) Modifies the original array
- How can you delay the execution of a function by 2 seconds?
- A)
setTimeout(myFunction, 2000) - B)
setDelay(myFunction, 2000) - C)
schedule(myFunction, 2000) - D)
delay(myFunction, 2000)
- A)
- Which method is used to find the largest value in an array of numbers?
- A)
Math.max() - B)
arr.max() - C)
arr.reduce(max) - D)
arr.largest()
- A)
- How do you access an HTML element with a specific ID using JavaScript?
- A)
document.getElementById('id') - B)
document.querySelector('#id') - C)
document.select('#id') - D)
document.getElement('id')
- A)
- What will
console.log(typeof []);output?- A)
array - B)
object - C)
list - D)
undefined
- A)
- Which property of the
navigatorobject is used to detect the browser version?- A)
navigator.version - B)
navigator.appVersion - C)
navigator.userAgent - D)
navigator.browserVersion
- A)
- What does
localStorageprovide in JavaScript?- A) Temporary storage of key-value pairs
- B) Persistent storage of key-value pairs
- C) Session-based storage of key-value pairs
- D) Network-based storage
- How can you execute a function once after a delay in JavaScript?
- A)
setTimeout() - B)
setInterval() - C)
requestAnimationFrame() - D)
queueMicrotask()
- A)
- Which method is used to merge two or more arrays into a single array?
- A)
concat() - B)
merge() - C)
combine() - D)
join()
- A)
- How do you update the text content of an HTML element?
- A)
element.textContent = 'new text'; - B)
element.innerHTML = 'new text'; - C)
element.setText('new text'); - D)
element.updateText('new text');
- A)
- What does the
catchblock in a try-catch statement do?- A) Catches exceptions thrown in the try block
- B) Executes code after the try block
- C) Executes code regardless of success or failure
- D) Initializes variables used in the try block
- Which method removes all elements from an array?
- A)
clear() - B)
empty() - C)
splice(0, arr.length) - D)
delete()
- A)
- How do you define a variable that is immutable (cannot be changed)?
- A)
const - B)
let - C)
var - D)
immutable
- A)
- Which operator is used to perform a bitwise AND operation in JavaScript?
- A)
& - B)
&& - C)
| - D)
|
- A)
- How do you create a new date object in JavaScript?
- A)
new Date() - B)
Date.create() - C)
new DateTime() - D)
Date.new()
- A)
- What does the
toFixed()method do?- A) Formats a number to a specified number of decimal places
- B) Converts a string to a number
- C) Rounds a number to the nearest integer
- D) Fixes the value of a number
- How do you create a new array from an existing one with some elements removed?
- A)
filter() - B)
slice() - C)
splice() - D)
reduce()
- A)
- Which method is used to iterate over the properties of an object?
- A)
forEach() - B)
map() - C)
Object.keys() - D)
Object.values()
- A)
- How do you check if an object has a specific property?
- A)
object.hasOwnProperty(property) - B)
property in object - C)
object.contains(property) - D)
object.includes(property)
- A)
- What does
Object.assign()do?- A) Copies properties from one or more objects to a target object
- B) Merges multiple objects into one
- C) Creates a new object with the properties of the source object
- D) Deletes properties from an object
- Which method will return the first index of a value in an array?
- A)
indexOf() - B)
findIndex() - C)
search() - D)
getIndex()
- A)
- What does the
Array.from()method do?- A) Creates a new array from an array-like or iterable object
- B) Converts an array into a string
- C) Merges multiple arrays into one
- D) Filters elements in an array
- How do you create a promise that resolves immediately with a value?
- A)
Promise.resolve(value) - B)
new Promise.resolve(value) - C)
Promise(value) - D)
new Promise(value)
- A)
- Which method will add a new element to the end of an array and return the new length?
- A)
push() - B)
pop() - C)
shift() - D)
unshift()
- A)
- How do you define a method inside a class in JavaScript?
- A)
method() {} - B)
function method() {} - C)
class.method() {} - D)
static method() {}
- A)
- Which method will return a new array with elements that meet a condition?
- A)
filter() - B)
map() - C)
reduce() - D)
forEach()
- A)
- How do you create an empty array in JavaScript?
- A)
var arr = []; - B)
var arr = {}; - C)
var arr = () => {}; - D)
var arr = new Array();
- A)
- What does the
toString()method do?- A) Converts a value to a string
- B) Extracts a substring from a string
- C) Formats a number as a string
- D) Parses a string into an integer
- Which method is used to get the last element of an array?
- A)
pop() - B)
slice(-1) - C)
last() - D)
peek()
- A)
- How do you check if a value is a number? – A)
typeof value === 'number'– B)isNumber(value)– C)value.isNumber()– D)Number.isInteger(value)
Here are the answers to the JavaScript multiple-choice questions:
- A) Curly braces
{ } - B)
function myFunction() {} - A)
var variableName; - C)
= - C)
// This is a comment - D)
Character - A)
string - A)
trim() - A)
parseInt() - B) Adds an element to the end
- B)
new - B)
=== - A)
JSON.parse() - B)
false - A)
arr[0] - C)
break - B)
11 - D)
const variableName = value; - D)
length - B) Returns a value from the function
- C)
x instanceof Y - C)
undefined - A)
var obj = {}; - D)
unshift() - A)
arr.concat(newElements) - B)
let - B)
false - B)
JSON.stringify() - B)
setInterval(myFunction, 5000); - A)
eval() - B) The object that is currently executing the code
- A)
isNaN() - B)
window.navigator - A) Converts a JavaScript object into a JSON string
- A)
Array.isArray(variable) - B)
33 - C)
Math.max(...arr) - C)
break - A)
pop() - A)
object.property - B)
false - A)
!= - A)
class MyClass {} - D)
throw - B)
1 - A)
new ClassName() - D)
input.value - C)
JSON.stringify() - A)
true - A)
object.method = function() {} - A)
push() - A)
3 - A)
str.includes(substring) - A)
join() - D)
new Promise(function(resolve, reject) {}) - B)
false - A)
variable() - B)
trimLeft() - A)
setTimeout(myFunction, 2000) - B)
new Array() - A)
splice(index, 1) - A)
indexOf() - D) All of the above
- A)
HELLO - A)
function myFunction(param = defaultValue) {} - C)
20 - A)
sort() - A)
new RegExp(pattern) - D)
static - A)
typeof object === 'function' - A) Returns a new array with elements that pass a test
- A)
setTimeout(myFunction, 2000) - A)
Math.max() - A)
document.getElementById('id') - B)
object - B)
navigator.appVersion - B) Persistent storage of key-value pairs
- A)
setTimeout() - A)
concat() - A)
element.textContent = 'new text'; - A) Catches exceptions thrown in the try block
- C)
splice(0, arr.length) - A)
const - A)
& - A)
new Date() - A) Formats a number to a specified number of decimal places
- B)
slice() - C)
Object.keys() - A)
object.hasOwnProperty(property) - A) Copies properties from one or more objects to a target object
- A)
indexOf() - A) Creates a new array from an array-like or iterable object
- A)
Promise.resolve(value) - A)
push() - A)
method() {} - A)
filter() - A)
var arr = []; - A) Converts a value to a string
- A)
pop() - **A)
typeof value === 'number'
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