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Home > Information Technology > Web Development > Javascript Basics

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25 Questions	Log in		Learn	00:00:00

1. What does the typeof operator return for an undefined variable?

Explanation: The typeof operator returns "undefined" for an undefined variable.
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"undefined"

"null"

"object"

"unknown"

Explanation: In JavaScript, a single-line comment is created using "//."
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// This is a comment

/* This is a comment */

' This is a comment '

3. What will be the result of the following code , console.log(5 + "5");?

Explanation: JavaScript performs type coercion, so it converts the number 5 to a string and concatenates it with the string "5."
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55

10

"55"

Error

4. What is the result of the expression 2 + "2"?

Explanation: JavaScript performs type coercion and converts the number 2 to a string before concatenating it with "2."
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22

4

"22"

Error

5. Which operator is used to compare two values for equality without considering their data types?

Explanation: The double equals (==) operator is used for loose equality comparison.
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==

===

=

!=

6. Which operator is used for strict equality comparison in JavaScript?

Explanation: The triple equals (===) operator is used for strict equality comparison, which checks both value and data type.
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==

===

=

!==

7. What is an anonymous function in JavaScript?

Explanation: An anonymous function is a function with no name.
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A function with no name

A function that returns an undefined value

A function with a random name

A function that has no parameters

8. How do you check the length of an array in JavaScript?

Explanation: To check the length of an array in JavaScript, you use the "length" property.
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lengthOfArray(array)

array.length()

array.length

getLength(array)

9. Which statement is used to throw an exception in JavaScript?

Explanation: The throw statement is used to throw an exception in JavaScript.
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throw

catch

try

finally

10. Which built-in object is used to display messages in a pop-up box in JavaScript?

Explanation: The alert method is used to display messages in a pop-up box in JavaScript.
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window

document

alert

console

11. Which of the following statements is used to exit a loop prematurely in JavaScript?

Explanation: The "break" statement is used to exit a loop prematurely in JavaScript.
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return

exit

break

continue

12. What is the result of the expression 5 > 3 && 2 < 4?

Explanation: The && operator returns true if both conditions are true, which is the case here.
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true

false

NaN

undefined

13. What is the correct way to declare a function in JavaScript?

Explanation: The correct way to declare a function in JavaScript is to use the "var" keyword followed by the function name and its definition.
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function = myFunction() {}

func myFunction() {}

var myFunction = function() {}

myFunction var() {}

14. What does the NaN value represent in JavaScript?

Explanation: NaN stands for "Not a Number" and represents an unrepresentable value in JavaScript.
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Not a Number

Null and Notable

No Answer

Negative Answer

15. What does JavaScript primarily allow you to do in web development?

Explanation: JavaScript is primarily used to add interactivity and behavior to web pages, making them dynamic.
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Create and style web pages

Perform server-side database operations

Add interactivity and behavior to web pages

Generate structured documents

16. Which function is used to remove an item from the end of an array in JavaScript?

Explanation: The pop() function is used to remove an item from the end of an array in JavaScript.
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push()

pop()

shift()

unshift()

17. What does the localStorage object in JavaScript allow you to do?

Explanation: The localStorage object in JavaScript allows you to store key-value pairs in the user's web browser.
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Access the user's camera

Store key-value pairs in the browser

Access the user's location

Display a modal dialog box

18. Which of the following is NOT a valid JavaScript data type?

Explanation: JavaScript does not have a data type called "Character." Instead, characters are represented as strings.
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Number

String

Boolean

Character

19. What does the this keyword refer to in JavaScript?

Explanation: In JavaScript, the this keyword refers to the current function or context.
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The current function

The previous function

The global object

The parent object

20. What is the purpose of the else statement in JavaScript?

Explanation: The else statement is used to specify an alternative condition to be executed if the initial condition is false.
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To specify an alternative condition

To create a loop

To define a function

To print text on the screen

21. What is the purpose of the setTimeout() function in JavaScript?

Explanation: The setTimeout() function is used to delay the execution of a function by a specified number of milliseconds.
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To execute a function after a specified number of seconds

To create a timer

To delay the execution of a function

To clear a timer

22. What is the purpose of the forEach method in JavaScript?

Explanation: The forEach method is used to loop through the elements of an array and perform a specified action for each element.
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To create a new array

To loop through the elements of an array

To sort an array

To filter an array

23. How can you convert a string to an integer in JavaScript?

Explanation: You can use the parseInt() function to convert a string to an integer in JavaScript.
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parseInt()

toInt()

strToInt()

castInt()

24. Which keyword is used to declare a variable in JavaScript?

Explanation: The "var" keyword is used to declare variables in JavaScript.
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