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1.How do you properly check if a variable is undefined in JavaScript?

var x;

if (x == null)

if (typeof x === 'undefined')

if (x === undefined)

2.What will be logged to the console in the following code?

var x = 1;
function foo() {
  console.log(x);
  var x = 2;
}
foo();

2

1

undefined

ReferenceError

3.What is the purpose of the `this` keyword in JavaScript?

Refers to the previous object

Refers to the current object

Refers to the parent object

Refers to the global object

4.Which of the following is NOT a valid way to declare a JavaScript variable?

var x = 10;

const y = 20;

let z = 30;

int w = 40;

5.What is the purpose of the `event.preventDefault()` method in JavaScript?

Stops the event from bubbling up the DOM tree

Prevents the default action of the event

Stops the event propagation to the parent elements

Disables the event completely

6.How do you check if an object has a specific property in JavaScript?

if (myObj.property)

if (myObj.property === undefined)

if (myObj.hasOwnProperty('property'))

if ('property' in myObj)

7.What is the purpose of the `typeof` operator in JavaScript?

Checks if a variable is defined

Returns the data type of a variable

Converts a variable to a specific type

Checks if a variable is null

8.What is the difference between `==` and `===` in JavaScript?

Both are strict equality operators

`==` is strict, and `===` is loose

`==` is loose, and `===` is strict

They are completely interchangeable

9.How do you declare a function in JavaScript?

var myFunction = function(){};

function myFunction(){}

both are correct

None of the above

10.What is the result of the expression `0 == false`?

null

FALSE

undefined

TRUE

11.Which of the following is a valid way to comment in JavaScript?

/* This is a comment */

// This is a comment

# This is a comment

-- This is a comment

12.What is the purpose of the `JSON.parse()` method in JavaScript?

Parses a string and returns an integer

Converts a JavaScript object to a JSON string

Converts a JSON string to a JavaScript object

Encodes a JavaScript object into JSON format

13.How would you round the number 7.25 to the nearest integer in JavaScript?

round(7.25)

Math.floor(7.25)

Math.ceil(7.25)

Math.round(7.25)

14.Which event is triggered when a user clicks on an HTML element in JavaScript?

onmouseover

onmousedown

onclick

onchange

15.How can you check the length of an array in JavaScript?

array.size()

array.count()

array.length()

array.size

16.What is the purpose of the `setTimeout` function in JavaScript?

Sets a timer for a specific time

Delays the execution of a function

Repeats a function at regular intervals

Clears the timer set by `setInterval`

17.What is the purpose of the `querySelector` method in JavaScript?

Selects all elements that match a specified CSS selector

Selects the first element that matches a specified CSS selector

Selects the parent element of a specified child element

Selects elements based on their tag name

18.How do you declare a constant variable in JavaScript?

let x = 10;

var x = 10;

const x = 10;

Both `const` and `let`

19.What does the following JavaScript code output?

console.log(2 + '2');

4'

22

NaN

22'

20.What is the result of the expression `3 == '3'`?

undefined

FALSE

TRUE

null

General JS I