UI development is the most sought up job in job portals today. With the new technologies coming up in UI development, job seekers need to upskill themselves.
Below are a set of top UI developer interview questions and answers that may be asked to UI developer job candidates. We will be discussing UI Developer Interview Questions based on three levels:
If you are a UI developer or aim to become one, the first step is to crack the interview to get into your job. You need to impress the interviewer by showcasing your skills and standing apart from the rest of the candidates with your knowledge and confidence.
So, before going for an interview, you should prepare well, brush up on all the concepts and practice practical skills.
UI Developer Interview Questions
1. Who are UI developers and what is their role?
A: You can start to answer by first defining what user interface. User interface is very important to meet users’ expectations and support the effective functioning of the site. A well-executed user interface helps ineffective interaction between the user and the machine through impressive visuals, clean design and responsiveness
The role of UI developer combines design skills and technical know-how and is responsible for the visual apprehension of the user interfaces.
The priorities of UI developers are: the interfaces to be functional, convenient and appealing.
2. How is the role of a UX developer different from a UI developer?
Ansible for designing visuals: Although these two roles often overlap, a UI developer is responsible for the interactive elements and something that helps users navigate their way through the product.
A user experience (UX) developer is responsible for creating and improving the quality of a user’s interaction with both the company and its product.
As an example, let’s consider a website with movie reviews. Even if the UI for finding a film is perfect( presence of all the required filters, options and other visual elements), the UX will be poor if a user wants information about a small independent release. The underlying database only contains movies from the major studios.
In short, we can say that UX is focused on the user’s journey to solve a problem; UI is focused on how a product’s surfaces look and function.
There is a restaurant analogy that many people use: UI is the table, chair, plate, glass, and utensils. UX is everything from the food to the service, parking, lighting and music.
3. Difference between a UI developer and a front-end developer?
A: Front-end developer creates client-side web interface using HTML, CSS, JavaScript and other common client-side technologies. The FE developer sees pages as a whole and a website as a combination of those pages. They make sure that the website functions properly, like all the website elements.
UI-Developer also uses HTML, CSS, JavaScript and other client-side technologies. For UI developers, more emphasis is on HTML and CSS. Their focus is on delivering more granular assets such as buttons, tooltips, and other modular pieces which will go into a larger, finished product.
The developer sees an asset as the individual CSS styles and pays more attention to how the asset will look, feel, behave in different contexts. UI developers may not even see a website as a whole but rather a collection of assets applied to pages. The UI developer makes sure that everything on the site is user-friendly and looks good.
4. Crucial skills for a successful UI developer?
A: A UI developer is a person who has an incredible eye for each and every detail and user experience.
Important programming skills that UI developers should include are HTML, CSS, JavaScript, AJAX, JSON, jQuery, Java, and SQL database development.
5. What is full form HTML and what is it used for?
A: HTML stands for HyperText Markup Language.
It is the most popular language for creating websites. It describes the structure of a Web page and consists of a series of elements. The elements of HTML tell the browser how to display the content.
6. What is CSS used for?
A: CSS is the language for defining styles for the Web pages, including colours, layout, and fonts. With CSS, one can define the layout and variations in display for different devices and screen sizes(laptop, tablet, mobile).
CSS can be used with any XML-based markup language, and it is independent of HTML.
7. Explain Javascript and its features?
A: JavaScript is an interpreted programming language that has object-oriented capabilities. It is lightweight. It allows one to build interactivity into otherwise static HTML pages.
Javascript is the most widely used for front end development like: Angular js, react js.
And is also used for backend development like: Node js, Nest js, Next js etc.
The various features of Javascript are:
- It is an interpreted programming language and is lightweight.
- It is designed for creating network-centric applications.
- It is integrated with Java and is complementary to it.
- It is integrated with HTML and is complementary to it.
- It is an open and cross-platform programming language.
8. Is Javascript a case sensitive language?
A: Yes, it is a case-sensitive language.
Case sensitive means that variables, function names, and any other identifiers must always follow a consistent capitalization of letters.
9. Tell us a few advantages of Javascript?
A: Javascript has less server interaction. One can easily validate user input before sending the page off to the server.
Javascript gives immediate feedback to the visitors; the user doesn’t have to wait for a page reload to see if they have forgotten to enter something.
Javascript increases the interactivity. One can create interfaces that react when the user hovers over them with a mouse or activates them with the keyboard.
10. Give an example of how to create and object in Javascript?
A: Below is an example of how to create an object in Javascript:
var example_object =
{
name: "obj1",
age: 10
height: 160
};
11. What is Semantic HTML?
A: Semantic HTML is used to give meaning to the code that we write, i.e., elements describe the meaning in human and machine-readable way.
Examples of semantic HTML5 elements are:<heade>, <footer>, <article>, <aside>,
<details>, <figure>, <figcaption>, <main>, <mark>, <nav>, <section>, <summary>, <time>.
12. What are HTML tags?
A: HTML tags are used to define how a web browser will format and display the content.
HTML tags consist of an opening tag, content and ending tag. There are some tags that are unclosed tags like <br> i.e. used for break line and <hr> that stands for horizontal rule.
A web browser can distinguish between an HTML content and a simple content with the help of HTML tags.
An HTML document in a web browser is read from top to bottom and left to right.
With the help of HTML tags one can create HTML documents and render their properties. One can use as many tags as per your code requirement, each HTML tag has a different property.
Syntax of tag is:
<tag> content </tag>
13. Detail out the layout of HTML.
A: HTML layout is the way to specify how the web page is arranged.
The different HTML5 elements which are used to define the different parts of a webpage are as follows:
- <header>: header for a document or a section is defined in this
- <nav>: defines a container for navigation links
- <section>: A section in a document is defined
- <article>: an independent, self-contained article is defined
- <aside>: example is a sidebar, that is aside of content
- <footer>: footer of a document is defined here
14. Describe the inline and block-level elements in HTML?
A. Block elements are that always start from a new line and take the full available container width.
It stretches itself to the available width of the container width. Some examples of the block-level elements are <div>, <p>, <img>, <section>.
Inline elements only take the width that is required to fit into the container.
Let us try to understand with the help of an example, take the flow of text on the page. When the line of the text has taken the full width of the container, it wraps into a new line and so on.
In the case of the inline element, it will only take that much space or width that it is needed for them. Few examples of Inline elements are <span>, <label>, <a>, <b>.
15. Explain the advantages of CSS?
A. Advantages of CSS are:
- Improved control of layout of the webpage.
- Style (CSS) files are kept separate from the HTML structure, this results in smaller file size.
- Smaller file size means the bandwidth is reduced resulting in faster loading time of the file.
UI developer Intermediate Questions
1. Explain responsive website
A: A website is called as responsive when it fits in all types of screen resolution device types. For example: laptop, mobile, tablet.
CSS media queries are used in order to re-arrange the elements, display or hide the elements from the user interface.
2. Does HTML require a compiler?
A: In general, HTML, CSS, and JavaScript are browser interpreted technologies.
Languages like C++, asp.net, PHP are not interpreted languages and need a compiler that will convert their code into machine language. HTML doesn’t need a compiler, it is an interpreted language and it is called a front-end language.
3. Explain the difference between window and document?
A: In JavaScript, a global object is used. Everything that runs under it is called a window.
A global object holds global variables, global functions, history and location under it.
Apart from it, Ajax, setTimeout, console and local storage are also under the window.
Since a document is the property of the window object, so it is also under the window.
4. What is the difference between this quartet of position properties: Relative, Absolute, Static, and Fixed.
A: Relative position means moving an element concerning its current position. Absolute position means an element is concerning its current position or the parent element’s position.
In DOM flow, Absolute elements don’t occupy space.
Static is sort of the default position.
Fixed position gives an element a fixed position relative to the device screen. As the name specifies, none of the fixed elements move during scrolling.
5. Explain web accessibility.
A: Web accessibility means providing website access for differently-abled people. WAI-ARIA helps differently-abled and disabled people use the web, navigate, understand and interact with it.
6. What is JavaScript Hoisting?
A: This is the one of the commonly asked UI Developer Interview Questions in an interview.
In JavaScript, we can access the variables after we have declared them.
If a variable is defined at the bottom of the script, but it is called before, the declaration, in this case, JavaScript throws an error that the variable is undefined.
In Javascript, hoisting is a mechanism where assigned variables and function declarations are “hoisted” to the top of their scope before executing code.
Therefore, functions get moved to the top of their range regardless of whether their scope is local or global.
7. What is event bubbling and event capturing?
A: Event propagation is defined as the order of events that happen on the element.
When the event is fired on, the element then bubbles up the DOM tree, meaning the child node will be called first and then the parent node. This is known as event bubbling.
Event capturing is opposite to event bubbling, i.e., here, first, the parent node is called up and then the child node.
8. Point out the differences between local storage, session storage, and cookies.
A: The difference between local storage, session storage and cookies can be explained as follows:
- Local storage offers the most substantial maximum storage limit and allows data storage with no expiration date.
- In Session storage, the stored data is associated with a session. It is same like local storage except that as soon as the user closes the tab or browser, the data disappears.
- Cookies store small size data that is to be sent back to the server. The size of data stored must be less than 4KB.
9. Explain the difference between XHTML, HTML4 and HTML5.
A: HTML stands for hypertext markup language and XHTML stands for extensible hypertext markup language.
XHTML is based on XML, whereas HTML is based on SGML. XHTML is considered strict as compared to HTML because it doesn’t allow users to get away with any coding or structure lapses.
XHTML is the cleaner and stricter version of HTML4 that is XML based. XHTML does not allow users any coding or structure lapses.
HTML5, is the latest version of HTML Web Standard with CSS & JavaScript.
10. Why should we use semantic elements?
A: We should use semantic elements as it increases the readability of the code.
It is the most important thing one will notice when looking at the first block of code using semantic elements. It is a small, simple example, but as a programmer, one could be reading through hundreds or thousands of lines of code, so the readability of code is very important. If the code is easier to read and understand, the job of the developer becomes much easier.
A code with semantic elements also has greater accessibility. Not only the developers but search engines and assistive technologies (like screen readers for users with a sight impairment) are also able to better understand the context and content of your website if semantic elements are used. This results in a better experience for the users of the website.
Overall, the usage of semantic elements leads to more consistent code.
When creating a header using non-semantic elements, different programmers( as they have different coding style) write this as <div class=”header”>, <div id=”header”>, <div class=”head”>, or simply <div>.
There are many ways that a developer can create a header element, and it all depends on the personal preference of the developer.
By creating and following a standard semantic element, it makes code easier for everyone to understand.
In HTML5, an upgraded version of HTML4, some new “semantic” elements are added. Some of us might still be confused as to why so many different elements don’t seem to show any major changes.
Example <section> and <article>
One can ask, “what is the difference? Both of these elements are used for sectioning a content and can definitely be used interchangeably.
It is basically a matter of which situation. HTML4 offered only one type of container element, which is <div>, whereas HTML5 provided us with <section> and <article> in a way to replace <div>.Although <div> is still used in HTML5
Conceptually both <section> and <article> elements are similar and interchangeable. To decide which of these elements one should choose, we should remember that:
The intention of an article is to be independently distributable or reusable whereas a section is a thematic grouping of content.
UI Developer Advanced Questions
1. Tell the difference between linking to an image, a website, and an email address??
A: Tags are used to link to an image.
The image should be specified in quotes using the source attribute, src in the opening tag <>.
The anchor tag is used for hyperlinking and <href> (HYPERTEXT REFERENCE) attribute is used to specify the link.
The anchor tag has the text to be hyperlinked and if the email is to be linked, the <href> specification would be “mailto:abc@here.com”
2. Define a few ways in which you can optimize a website’s assets?
A: A website’s assets can be optimized by following methods:
- File concatenation,
- File compression
- CDN Hosting
- Offloading assets
- Re-organizing
- Refining code
3. What are the ways in which we can reduce the page load time?
A: The ways in which we can reduce the page load time are:
- Reducing image sizes
- Removing unnecessary widgets
- HTTP compression can be used, CSS should be placed at the top and script references should be placed at the bottom or in external files
- Reduce lookups
- Minimize redirects
- Caching
4. What are the important things one must keep in mind when designing or developing for multilingual sites?
A: While designing or developing for multilingual sites, below things should be followed:
- The default language should be set, using unicode encoding,
- We should use the ‘lang’ attribute and should be aware of standard font sizes and text direction
- language word length should be taken into account as it may affect layout.
5. Explain the functioning of floats?
A: The float is a property that can have one of four values, it pushes the element to the left or right
- Inherited: This means that the element inherits the parent’s float value
- None: The element doesn’t float, this is the default value
- Left: This means that the element floats to the container’s left
- Right: This means that the element floats to the container’s right
6. What are the plugins available in the Bootstrap jQuery plugin library.
A: There are many plugins present in Bootstrap plugin library as below
- Alert
- Affix
- Button
- Carousel
- Collapse
- Dropdown
- Modal
- Popover
- Scrollspy
- Tab
- Tooltip
7. Suppose while executing the code an error is thrown, what’s the difference between require() and include()?
A: include() and require() are the commands. Include() command if it fails raises a warning whereas require() command when fails raises a fatal error.
8. Explain the difference between reset.css and normalize.css?
A: Reset.css, as the name indicates, eliminates all browser default styles, such as margin, padding, border.
On the other hand, as the name normalize indicates, normalize.css sets a standard book-like appearance (e.g., bold headings, margins between two paragraphs, common font) across all browsers. It does not reset the styles, it just normalizes them.
9. Explain what is an AJAX request, and how would you use an AJAX request?
A: Full form of AJAX is asynchronous JavaScript and XML. It is a client-side process that is written in JavaScript.
Using AJAX we can get or post data from a remote server without needing to reload the page.
10. Write a Javascript code snippet, to find specific objects in an array of objects?
A: We can use Javascript “find” method for the same:
let customers = [
{ id: 0, name: 'jane' },
{ id: 1, name: 'tim' },
{ id: 2, name: 'maria' }
];
let customer = customers.find(cust => cust.name === 'maria');
console.log(customer);
--> { id: 2, name: 'maria' }
11. Write a Javascript code snippet, to filter an array of objects based on condition.
A: Below is the code snippet using Javascript “filter” function:
let data = [
"files/dir1/file1",
"files/dir1/file2",
"files/dir2/file1",
"files/dir2/file2"
];
let filteredData = data.filter(path => path.includes('dir2'));
console.log(filteredData);
--> [ 'files/dir2/file1', 'files/dir2/file2' ]
12. Write a simple function to indicate whether or not a string is a palindrome. The function should return a Boolean value.
A: Below is the code snippet of function that will return true if string is a palindrome; otherwise, it returns false.
function isPalindrome(string) {
string = string.replace(/\W/g, '').toLowerCase();
return (string == string.split('').reverse().join(''));
}
For example:
console.log(isPalindrome("level")); // logs 'true'
console.log(isPalindrome("levels")); // logs 'false'
This brings us to the end of the blog on the top UI Developer Interview Questions. We hope that this helps you ace your upcoming interview sessions. All the best for the interview!
If you wish to learn more such concepts, take up UI design courses and enhance your knowledge to power ahead your career.
