Question 1

Explain JavaScript cookies.

Accepted Answer

Cookies are data that contain information about users' preferences and is stored on their computers. So that whenever the user visits the same website, it can read the cookie that is saved in the user's file. This data can be accessed by the web server or the client's computer.

Question 2

How can we read and delete a cookie using JavaScript?

Accepted Answer

We can create a cookie using document.cookie. For deleting, we need to set the expiration date to the past.

Question 3

When do we need an escape character in JavaScript?

Accepted Answer

When we include special characters like single and double quotes, apostrophes, and ampersands in our code, we use this escape character.

Question 4

How can we detect the operating system on the client machine?

Accepted Answer

Using navigator.appVersion, will return the string that helps detect the version information of the client browser.

Question 5

What is the difference between JavaScirpt and Java?

Accepted Answer

JavaScript is used with HTML and CSS to add interactivity on the client side. It runs in the browser and does not go through compilation before running the application code. Java is a compiled language used to build diverse, standalone applications. It is platform-independent and runs on different operating systems.

Question 6

How is an alert box different from a confirmation box?

Accepted Answer

The alert box is an OK button to inform the user about the agreement. The confirmation box has two buttons, i.e., OK and cancel buttons.

Question 7

What is a class in JavaScript?

Accepted Answer

Class is the syntactic sugar used in constructor functions. It can inherit properties and methods from other classes by using the extended keyword.

Question 8

What are primitive data types in JavaScript?

Accepted Answer

Primitive data types are boolean, undefined, null, brignt, number, and string. This data type is used to display only one value at a time.

Question 9

Which function is used to remove duplicates from an array in JavaScript?

Accepted Answer

We can do this using two functions: the filter() method and the for loop. When we use the filter() method, arguments like an array, the current element, and the index of the current element are required. While using the for loop, we use an empty array to store all the repeating elements.

Question 10

When do we use void(0) in JavaScript?

Accepted Answer

We use this to prevent page reload and pass the undefined (void) as a primitive value.

Question 11

What are the three different types of errors in JavaScript?

Accepted Answer

Three errors are syntax errors, logical errors, and runtime errors: When a programmer makes a mistake in the program's syntax, it is called a syntax error. A logical error is when the program does not provide the expected output.

Question 12

What are the two different types of groups of data types used in JavaScript?

Accepted Answer

Reference type and primitive type: where the difference type is used with complex data that includes data and strings. Primitive data types include numbers.

Question 13

What problems are encountered with global variables?

Accepted Answer

With this kind of variable declaration, debugging and testing become more challenging. Also, there is a clash between local variable names and global variables.

Question 14

How can we read and write the properties?

Accepted Answer

By using the dot(.) operator, we can read and write the properties in JavaScript.

Question 15

What is the difference between "==" and "===" operators in JavaScript?

Accepted Answer

These are the comparison operators used to compare the values or data types. “==” is used to compare only values, and "===" is used to compare values and data types in JavaScript.

Question 16

What do you know about the arrow function?

Accepted Answer

Arrow functions are a concise way to write JavaScript functions. This function is introduced in the ES6 version of JavaScript.

Question 17

What is the difference between prototypal and classical inheritance?

Accepted Answer

In prototypal inheritance, objects are directly inherited from their parent object. It forms a chain of objects, and there is no concept of class. Whereas classical inheritance is like traditional inheritance, where it works like a hierarchy. An object is created through a class.

Question 18

Why do we use NULL in JavaScript?

Accepted Answer

We use this null value to represent the variable that has no assigned value.

Question 19

How can we use a browser to debug?

Accepted Answer

Using the F12 key on the keyboard, we can open debugging mode in any browser and simply tap over the console, and then our output will be displayed.

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