Intermediate-Level JavaScript Interview Questions and Responses (2025)

In the world of web development, JavaScript continues to be a cornerstone technology. Here's a roundup of some key JavaScript concepts, from cookies to loops, functions, and exceptions.

JavaScript Cookies

JavaScript Cookies are small pieces of data stored by the browser on the client machine. To create a cookie, you just need to assign a string value to the object. For example:

To read a cookie, you can use the string. To delete a cookie, set the attribute of the to a time in the past, and ensure that the correct cookie path is defined.

Pop-up Boxes and Cookies

Alert, Confirm, and Prompt are the types of pop-up boxes available in JavaScript. An alert box displays only one button which is the OK button, while a Confirmation box displays two buttons OK and Cancel.

Loops and Functions

A for loop provides a concise way of writing the loop structure. It is similar to the while loop, but it initialises the counter variable and checks the condition at the beginning of each iteration.

The loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. A do-while loop is similar to while loop with the only difference that it checks the condition after executing the statements.

The function is used to remove focus from the selected element. The function, on the other hand, is used to set focus on the selected element.

Functions and Methods

The and functions are used for reading and writing operations, respectively. The function is used to convert the string to an integer.

The function encodes a string so that it can be transmitted to any computer in any network which supports ASCII characters. Escape characters are required when working with special characters like single and double quotes, apostrophes, and ampersands. The escape character is the backslash .

Exceptions

The , , and keywords are used to handle exceptions in JavaScript. When an error occurs in a try block, the code in the catch block is executed. The keyword is used to intentionally raise an exception.

Objects

To create a generic object in JavaScript, use: . You can also create an object using a constructor function.

Operating System Detection

The or property can be used to detect the operating system on the client machine.

Scope

JavaScript does not have a concept-level scope. The variables declared inside any function have scope inside the function.

Conclusion

These are just a few of the many concepts in JavaScript. From cookies and loops to functions, methods, exceptions, and objects, JavaScript offers a rich and powerful set of tools for web development. As for the future, potential advanced-level JavaScript candidates may include those participating in programs like the Constructor Academy's Full-Stack Web Development Bootcamp, which covers advanced JavaScript topics.