10 most important front-end developer interview questions and answers

Are you a front-end developer looking to build your career? Or, are you a recruiter hunting for exceptionally talented front-end developers? If the answer to at least one of them is yes, you have come to the right place. This list of meticulously selected front-end developer interview questions can help you in acing your front-end developer interview, regardless of whether you are a front-end developer or a recruiter looking for one.

Last updated on Mar 22, 2023

In this extremely fast-paced and technically demanding reality that we live in, any user demands a seamless experience. This is exactly where a front-end developer comes in clutch. A front-end developer deals with everything that the user experiences directly: all the images, the colors, the text, the buttons, etc. front-end developers optimize and design the front-end of any application to cater to the user. This is exactly why the demand for proficient front-end developers is extremely high in today’s world. Therefore, if you want to work as a front-end developer in a well-established US-based MNC, it is not easy to crack the front-end developer interview. The front-end developer interview questions are extremely tough to answer and, for interviewers, to prepare the perfect questions.

However, fear not, as this carefully crafted and handpicked list of essential front-end developer interview questions will help you prepare for your big interview. Go through these front-end interview questions, whether you are the candidate who's looking for a front-end developer job, or a recruiter, who wants to create the perfect front-end interview questions to hire the best talent for their company.

Front-end interview questions and answers


What is the purpose of using doctypes in HTML?

You've probably noticed a declaration before the tag in an HTML page. The element in HTML is used to tell the browser what version of HTML is being used in the page. This document type declaration is called (DTD).

isn't technically a tag or element; it's simply a directive to the browser about the document type. It's a null element that doesn't have a closing tag and can't have any content inside of it.

The doctype declaration varies depending on the HTML version.


Explain sessionStorage, localStorage, and cookies.

Session Storage: As the name implies, this data is saved until the session or tab is closed; however, it is not removed when the browser is reloaded. This information is kept on the client-side and cannot be sent to the server.

LocalStorage: This data is kept locally on the client's machine. This data has no expiration date; however, it is restricted to string data only. You can use Javascript and HTML to access local data, but you cannot send them to the server. Although data in local storage has no expiration date, the user can choose to delete it.

Cookies: Cookies transmitted back to the server must be less than 4KB in size. When a further XHR request is performed, the data is returned. Although they are intended for server-side reading, they can also be accessed from the client.


How will you navigate the DOM with JavaScript?

Either getElementById or querySelector may be used to obtain a DOM node. Then, by calling .childNodes you may receive all of its children (note: childNodes does not return an Array, but a NodeList). To traverse the DOM, you can iterate through the childNodes by calling childNodes on each one of them. You may retrace your steps by looking at the parentNode of any node.


What are the disadvantages of using CSS preprocessors?

Some significant disadvantages of using CSS preprocessors are:

  • Compilation times may take longer than expected. This is because you must translate every SASS file to CSS before building it.
  • Because it combines several CSS files, the primary file might get rather huge. This increases the time it takes to execute a request.
  • There is a longer learning curve since the user must have a thorough grasp of the preprocessor before using it.


Differentiate between synchronous and asynchronous functions?

Synchronous methods: Synchronous functions prevent the application from running until the file operation is completed. Blocking functions is another name for these functions. The last argument in synchronous methods is File Descriptor. A file descriptor is a reference to files that have been opened. It's a number or a file reference id returned after using the fs module's fs.open() function to open the file. By putting "Sync" to the function name, all asynchronous methods may be made to run synchronously.

Asynchronous functions do not stall the program's execution, and each instruction is performed after the one before it, even if the prior command hasn't computed the result. The preceding command keeps running in the background until it is complete and then loads the result. As a result, these functions are referred to as non-blocking functions. The last parameter expected is a callback function. Asynchronous functions are often favored over synchronous functions because they do not prevent the program from running until it has completed processing, whereas synchronous functions do.


Talk about Load Balancing.

Load balancing is a way of allocating and processing requests across several devices rather than a single device. This guarantees that the load is distributed efficiently and does not rely on a single location.

Round Robin is the most often utilized load balancing technique. The requests are dispersed over a collection of servers in this approach. The algorithm distributes requests to the servers and then returns to the top to restart the process.


What do you understand by semantic HTML?

The right use of HTML to reinforce the meaning of material on a web page, rather than only specify its look, is known as semantic HTML.

Search engines, screen readers, and other user devices can employ semantically valid HTML to assess the importance and context of web content. Appropriate HTML components are chosen based on their intrinsic meaning rather than how they seem aesthetically on a produced web page in order to reflect the essence of information effectively.


Offer some suggestions regarding how to fix a browser-specific styling issue.

  • Using server-side rendering, we can construct a unique stylesheet for each browser.
  • Another option is to use a package such as Bootstrap, which already contains the code to deal with the browser-specific styling problem.
  • Reset and Normalize CSS are also options.
  • Many third-party plugins include libraries to help with browser style.


What do you know about reflow? Mention some ways to avoid it.

When one element's layout, window size, or other properties are altered, the position of all subsequent elements changes as well. This, in turn, impacts the page's flow, which is referred to as reflow.

You may avoid reflow by using the following methods:

  • It's best to avoid using several inline styles.
  • Avoid using tables in your design.
  • Only use animations on fixed or absolute items.


What do you think, are window.onload and document.onload fired simultaneously?

No, window.onload and document.onload are not fired simultaneously. When the DOM is ready, Document.onload is called. This can happen before or after the pictures, scripts, and other information have been loaded.

Window.onload, on the other hand, is only invoked after the DOM is fully loaded and ready with all content, including images, scripts, and CSS.

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Wrapping up

With these well-crafted front-end developer interview questions, you are now very aptly equipped to design and answer any questions regarding front-end development. However, these front-end developer interview questions only cover the technical aspect of the interview. An interview doesn’t just gauge the technical prowess of a candidate. Apart from preparing these front-end developer interview questions, you would also need to work on your soft skills and social life as a front-end developer. As a recruiter, your responsibility is to ask questions, apart from the front-end interview questions, on how a candidate manages their time, their personal and collaborative projects, and how well their team synergy is to find the perfect fit for your company.

You can work with Turing if you're a recruiter looking to hire from the top 1% of front-end developers. If you're an experienced front-end developer searching for a new opportunity, Turing.com is a great place to start.

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