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60+ Front End Developer Interview Questions and Answers

60+ Front End Developer Interview Questions and Answers
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Interviewing a front-end developer may be challenging. However, with the right set of questions, you can easily make out whether the candidate is a "position player" (a specialist in one position) or an "athlete" (a multi-tasker). It is crucial to ask the most relevant questions pertaining to the profile to select the right candidate.

Here are the 60+ front-end developer interview questions to help you determine whether the candidate will add value to your organization or not. This comprehensive list is a mix of questions for beginner-level front-end developers and expert-level front-end developers.

Here we go….

Most Frequently Asked Front End Developer Interview Questions:

Q-1 What are the fundamental skills required to be a front-end developer?

*A good front-end developer should be fluent in the following languages: CSS, JQuery, HTML, and JavaScript. Besides, a front-end developer should also be familiar with Content Management Systems like Drupal, Joomla, WordPress, and PHP, and OOP. Expertise in cross-browser testing. Furthermore, knowledge of SEO and tools such as Flash and Dreamweaver is used to present web-based knowledge to end-users.

Q-2 What is clear, and how is it used?

A clear is used when an element, such as a float, does not need to wrap around another element.

Q-3 Which HTML5 features are your favorites, and how have you used them in your front-end development projects?

*Look for in-depth knowledge of HTML5 features and a clear explanation of how the applicant used HTML5 in previous projects, and creative use of HTML5 features.

Q-4 What is the use of clear in CSS?

The clear CSS (Cascading Style Sheets) property specifies whether an element should be moved beneath (cleared) floating elements that come before it. Clear applies to both floating and non-floating elements.

Q-5 What is the distinction between HTML XHTML and XML?

HTML stands for HyperText Markup Language, whereas XHTML is an abbreviation for Extensible HyperText Markup Language. HTML and XHTML are both languages used to create web pages. HTML is an SGML-based language, whereas XHTML is an XML-based language. They are similar to the two sides of the same coin. To conform to XML standards, XHTML was derived from HTML.

Q-6 How do you make sure your web design is user-friendly?

There are several ways to ensure user-friendly web designs, including providing detailed information, creating intuitive navigation, selecting the appropriate color scheme, including strong calls to action (CTAs) on your pages, beefing up your contact page, and so on.

Q-7 How do you make the structure of CSS and JavaScript easier for other developers to understand?

A front-end developer should talk about how they organize their code and comment on it. They must explain how they use notes in their programming process to explain the steps they have taken, ensuring that collaborators understand each step efficiently.

Q-8 What are the features of Three.js?

Three.js has many features, including Effects and Animations, Scenes and Cameras, Data loaders and Shaders, Geometry and Objects, Debugging and Virtual Reality, Utilities, and Materials, Support, and so on.

Q-9 What are your thoughts on CSS float?

The float CSS property positions an element to the left or right of its container, allowing text and inline elements to wrap around it. The element is removed from the page's normal flow, but it remains a part of the flow (in contrast to absolute positioning).

Q-10 What is the difference between internal and external JavaScript?

In Internal JavaScript, code is placed in the HTML page's head and body sections. While in External Javascript, the .js extension is used to store JavaScript code in a separate external file (Ex: external. js).

Related: Software Developer vs Software Engineer Differences

Q-11 Explain the significant differences between Prototypal and Class inheritance?

A class is similar to a blueprint. The traditional method for creating an object is to define its structure with a CLASS declaration and then instantiate that class to create a new object. In contrast, prototypal inheritance is about objects. Objects inherit properties from one another.

Instead of defining the structure through a class, prototypal inheritance simply creates an object.

Q-12 What do you understand about the CSS Rule?

A CSS rule is a collection of one or more CSS properties that will be applied to one or more target HTML elements. A CSS rule is made up of a CSS selector and a collection of CSS properties. The CSS selector specifies which HTML elements should be targeted by the CSS rule.

Q-13 What are the HTML5 building blocks?

An HTML document consists of the following basic building blocks:

  • more semantic text markup
  • new form elements
  • new data storage
  • video and audio
  • new JavaScript API
  • canvas and SVG
  • new communication API
  • geolocation API
  • web worker API

Q-14 What, according to you, is Sass?

*Check on the candidates' knowledge about Syntactically Awesome Style sheets.

Sass is a scripting language used as a preprocessor that can be interpreted or compiled into Cascading Style Sheets. The scripting language is called SassScript. Sass is made up of two syntaxes. The original syntax, known as "the indented syntax," employs a Haml-like syntax.

Q-15 Explain the main difference between a unit test and a functional test?

The testing process is built around the unit and functional testing. The main distinction between the two is that Unit testing is carried out by the developer during the development cycle, whereas Functional testing is carried out by the tester during the level of system testing.

Also See: Software Developer Skills for Freshers to Enter The Software Industry

Q-16 What is the difference between "resetting" and "normalizing" CSS? Which one would you pick?

Normalize CSS is primarily a set of styles that its author thought would look good and be consistent across browsers. Reset removes styling from elements, giving you more control over the styling of everything.

Q-17 How will you do it if you want to use an arbitrary object as the value of this?

There are at least three ways to accomplish this using bind, call, and apply.

Q-18 What do you understand about HTML Meta tags?

The meta> tag defines metadata about an HTML document.... meta> tags are always placed inside the head> element and are generally used to specify a character set, page description, keywords, document author, and viewport settings. Metadata will not be displayed on the page, but machines can parse it.

Q-19 How would you go about implementing the moveLeft animation?

An animation can be implemented as a series of frames, typically making minor changes to HTML/CSS properties. Here is the example:
let timer = setInterval(function() {
if (animation complete) clearInterval(timer);
else increase style.left by 2px
}, 20); // change by 2px every 20ms, about 50 frames per second

Q-20 How would you write a method on an instance of a date that will give you the next day?

Date.prototype.addDays = function(days) {
var date = new Date(this.valueOf());
date.setDate(date.getDate() + days);
return date;
}
var date = new Date();
console.log(date.addDays(5));

Q-21 Explain the difference between div and span?

Both span and div are generic HTML elements that are used to group together related parts of a web page. They do, however, serve different purposes. A div element is used for page element block-level organization and styling, whereas a span element is used for inline organization and styling.

Q-22 What criteria are used to match descendant CSS selectors?

In CSS, a descendant selector is any selector that has white space between two selectors that do not have a combinator. For example:

ul li { }
header h2 { }
footer a { }
.module div { }
#info-toggle span { }
div dl dt a { }
ul li { } in the example means “any list item that is a descendant of an unordered
list.”

Descendant means anywhere in the DOM tree that is nested

within it.

It could be a direct child or a five-level descendant,

but it is still a descendant. This is not the same as a child combinator

(>), which requires the element to be at the next nested level down.

Q-23 What do you understand about grid layout?

The grid layout is a confluence of rows and columns that simplifies web page design by eliminating the need for floats and positioning.

Q-24 How does one go about making a website responsive?

Responsive web design is highly important for a successful business nowadays. The layout is the first thing to consider when creating a responsive website, followed by media (video and images). Following the media, we must consider typography.

Q-25 What is ReactJS?

React is a JavaScript library that allows you to create fast and interactive user interfaces for web and mobile applications.

Q-26 How would you go about implementing currying for any function?

Currying is a sophisticated method of working with functions. It is used not only in JavaScript but also in other languages.

Currying is a function transformation that converts a function from being callable as f(a, b, c) to being callable as f(a)(b) (c).

Currying does not invoke a function. It simply transforms it. Here is an example:

function curry(f) { // curry(f) does the currying transform

return function(a) {

return function(b) {
return f(a, b);
};
};
}
// usage
function sum(a, b) {
return a + b;
}
let curriedSum = curry(sum);
alert( curriedSum(1)(2) ); // 3

Q-27 What exactly is domain pre-fetching, and how does it improve performance?

Prefetching enables a browser to silently fetch the resources required to display content that a user may access in the near future. The browser can store these resources in its cache, allowing it to deliver the requested data more quickly.

Q-28 What are the advantages of REST web services?

Advantages of REST web services include:

  • The learning curve is low because it is based on the HTTP protocol.
  • Text, XML, JSON, image, and other data transfer technologies are supported.
  • Because there is no contract between the server and the client, the implementation is loosely coupled.
  • REST is a lightweight protocol, and REST methods can be easily tested in a browser.

Q-29 What's the difference between reset.CSS and normalize.CSS?

reset.css removes all default styles, whereas normalize.css keeps some necessary styling.

Q-30 How would you go about implementing modularity in CSS?

Modular CSS is a methodology, philosophy, or approach to breaking down webpage styling into smaller independent components that are consistent, reusable, and retain visual integrity in any part of the webpage. CSS modules, for example, are created using a set of guidelines (or principles) to create a collection of reusable building blocks.

Q-31 What is cross-browser compatibility?

Cross Browser Testing is a type of testing that determines whether an application works as expected across multiple browsers and degrades gracefully. It is the process to ensure that your application is compatible with various browsers.

Q-32 Explain the differences between null and undefined?

A Null is an object with no value whereas, Undefined is a type. Type of null; // “object” type of undefined; // “undefined”

Q-33 What is Event Delegation?

Using event propagation to handle events in the DOM at a higher level than the element from which the event originated is referred to as event delegation. It allows you to avoid adding event listeners to specific nodes and instead add a single event listener to a parent element.

Q-34 What do you understand by Load Balancing?

The systematic and efficient distribution of network or application traffic across multiple servers in a server farm is referred to as load balancing. Every other load balancer stays between client devices and backend servers, receiving and distributing incoming requests to any server that can fulfill them.

Q-35 What exactly does SOLID mean? What are its guiding principles?

SOLID is a set of design principles used in the development of object-oriented software. SOLID is an acronym that stands for five fundamental design principles: single responsibility, open-closed, Liskov substitution, interface segregation, and dependency inversion.

Q-36 What is the best CSS hack you've ever done?

Here the candidate is expected to explain his/her experience. Make sure it is genuine and effective.

Q-37 What do you understand by lazy loading?

Lazy loading is a design pattern mainly used in computer programming to postpone object initialization until it is needed. If used correctly and correctly, it can contribute to program performance. Furthermore, it is a loading code that is only used when the user requires it. For example, there is a button on the page that, when pressed, reveals a different layout. As a result, there is no need to load code for that layout on the first-page load.

Q-38 What is the function of Python float?

The Python float() function converts a number stored in a string or integer to a floating-point number or a decimal point number. Python Floats are helpful for any process that requires precision, such as scientific notation.

Q-39 Is there an effect of margin-top or margin-bottom on inline elements?

Inline elements are unaffected by top and bottom margins because they flow with the content on the page. An inline element can have left and right margins/padding but not top and bottom margins because it would restrict the flow of content.

Q-40 What exactly is a CDN, and why should you use one?

Content Delivery Network, also known as CDN, is a widely distributed platform of servers that reduces the physical distance between the server and the user to help minimize delays in loading web page content. This allows users all over the world to view the same high-quality content without having to wait for it to load.

Q-41 What exactly is ClickJacking?

Clickjacking is a kind of attack in which a user is tricked into clicking on a webpage element, which is either invisible or disguised as another element. Users may unknowingly download malware, visit malicious web pages, provide credentials or sensitive information, transfer money, or purchase products online as a result of this.

Q-42 Do you think CSS rule names are case-sensitive?

CSS selectors, including class and ID selectors, are generally case-insensitive. However, HTML class names are case-sensitive.

Q-43 How do you clear the sides of a floating element?

CSS clear regulates the behavior of the floating element by preventing consecutive elements from overlapping over it.

The value of the property clear specifies which side of the floating element should not float. The clear property can have the values none, left, right, inherit, inline-start, and inline-end.

Q-44 What is a Callback Function?

A callback, commonly known as a "call-after" function in computer programming, is any executable code that is passed as an argument to other code and is expected to call back the argument at a specified time.

Q-45 What exactly is Ajax?

AJAX or Asynchronous JavaScript and XML allow applications to send and receive data concurrently from and from a server without refreshing the page. This means one can update parts of a web page without having to reload the entire page. For example, even if you haven't refreshed the web page, new Gmail messages arrive and are marked as such.

Q-46 What is DOCTYPE Reference, and significance of the HTML DOCTYPE?

A Doctype declaration is a reference to a Document Type Definition (DTD). DOCTYPE tells the web browser what version of the markup language the page is written in. Before the tag, the DOCTYPE declaration should be the first thing in your HTML document. It specifies markup language rules so that a browser can correctly interpret the content.

Q-47 What exactly is createDocumentFragment, and why might you use it?

The createDocumentFragment() method generates an imaginary Node object with all of the Node object's properties and methods. It allows you to extract parts of documents, add, change or delete some of the content, and then re-insert it into the document.

Q-48 What exactly is the distinction between Block, Inline, Inline-block, and Box-sizing?

  • The default is inline. For example, a span> is an inline element.
  • Block is displayed as a block element, such as div> or p>.
  • Inline-block denotes an element that serves as an inline-level block container.
  • The box-sizing property displays the browser's sizing properties.

Q-49 What do you understand by Event Bubbling?

Event bubbling is a form of event propagation in which the event occurs first on the most profound target element. It allows all events in the child nodes to pass to the parent nodes automatically. This method is faster because the code only needs to circumnavigate the DOM tree once.

Q-50 Why don't CSS selectors mixed with cases apply styles?

It is because HTML ID and classes are case-sensitive.

Q-51 What is user-centered design? How is it important?

UCD or User-centered design is an adaptive design process in which designers focus on the users and their needs at each stage of the design process. It aids in understanding users' needs and preferences regarding product features, tasks, goals, user flow, and so on.

Q-51 What is the main difference between a host object and a native object?

Host Objects are objects that are provided by a specific environment. Native Objects, on the other hand, are standard built-in objects provided by JavaScript.

Q-52 Does padding-top or padding-bottom affect inline elements?

Browsers treat inline elements differently when it comes to margins and padding. Space to the left and right of an inline element can be added, but adding height to the top or bottom padding or margin is not possible. Inline elements can exist within block elements.

Q-53 What is CoffeeScript?

CoffeeScript is a programming language that can be translated into JavaScript. It adds syntactic sugar inspired by Python, Ruby, and Haskell in an effort to improve the brevity and readability of JavaScript.

Q-54 When and why should one use Webpack?

Webpack gives you control over how to treat different assets it encounters. For example, you can choose to inline assets to the JavaScript bundles to avoid requests. Webpack also enables developers to use techniques such as CSS Modules to integrate styling with components while avoiding issues of standard CSS styling.

Q-55 What is jQuery? What are the benefits of using jQuery?

jQuery is a compact, fast, and feature-rich JavaScript library that is contained in a single.js file. It simplifies the life of a web developer. It offers a plethora of built-in functions that allow you to complete a variety of tasks quickly and easily. It advantages include:

  • jQuery's online API documentation is excellent.
  • jQuery provides excellent cross-browser support without the need for additional code.
  • jQuery is unobtrusive, allowing for the separation of concerns by separating HTML and jQuery code.

Q-56 How can you tell if one element is a child of another?

The following is the code to determine whether the two elements of parent-child relationships are present.
function isChild (obj,parentObj){
while (obj != undefined && obj != null && obj.tagName.toUpperCase() != 'BODY'){
if (obj == parentObj){
return true;
}
obj = obj.parentNode;
}
return false;

Q-57 What are the advantages of using Coffee Script over JavaScript?

CoffeeScript includes a plethora of lightweight extensions, such as Ruby string interpolation and Python style list comprehension.

  • It also allows you to express your program with far less code than JavaScript.
  • It improves the readability of even good JavaScript code.
  • CoffeeScript makes performing everyday tasks easier than JavaScript.

Q-58 What is the distinction between classes and IDs?

Classes and ID selectors are both used as CSS-style hooks. The IDs are commonly used to style elements that appear only once on a page, such as a navigational menu. Classes are used to style various elements in the same way, such as the presence of links.

Q-59 Explain how variables in Coffee Script differ from variables in JavaScript.

Before we can use a variable in JavaScript, we must declare and initialize it (assign value). In contrast to JavaScript, there is no need to use the var keyword when declaring a variable in CoffeeScript. We simply create a variable by assigning a value to a literal.

Q-60 What does the term ternary mean? Why is it referred to as a ternary expression?

Ternary?: is a three-argument operator that represents a conditional expression. It is a one-line shorthand for an if-then statement, also known as the Ternary operator or Conditional operator.

Q-61 Explain the nuances between cookies, session storage, and local storage?

Cookies enable applications to store data in the browser of a client. Applications can use the session storage property to store data until the window is closed. The local storage property allows applications to store data indefinitely.

Q-62 What is a Thread-Local object in Python Flask?

A thread-local is the object stored in a dedicated structure and is associated with the current thread id. Flask uses thread-local objects internally so that the user does not have to pass objects from one function to another within a request in order to remain thread-safe. Furthermore, Thread local storage conducts one's logger's global context but only within the current thread. This approach is useful, but it requires a valid request context for dependency injection or when attempting to reuse code that uses a request-specific value.

Wrapping it up…..

These are the 60+ front-end developer interview questions. All the questions mentioned above are the most frequently asked interview questions for front-end developers. This is a comprehensive list that contains questions for beginner-level front-end developers and expert-level front-end developers. If you're an applicant, this list of questions can help you prepare for your next interview.
Besides, this list is helpful for the managers as well. They will be able to check the in-depth knowledge of the candidate with the help of these questions.
Hopefully, this comprehensive list of questions helps you crack your next interview! All the best for your next interview…. ☺

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