CSS, fully known as Cascading Style Sheets, is a style sheet language used by front-end developers to create a consistent outlook and feel for all application’s webpages. It allows them to enjoy the necessary flexibility in website design. You should be ready to answer questions touching on CSS if you are interested in a front-end development job.
This article will put together 25 frequent questions in CSS interviews to give you an easy time as you prepare for a new role. Most of these questions are technical, and therefore, you should be good at the technical aspect of your job. Take a look at the following questions:
1. What Are The Advantages Of CSS?
CSS has several advantages, which explains its popularity among developers and software engineers. It offers better website speed, allowing the efficient functioning of websites. It is also easier to maintain as compared to other languages. Other advantages are its consistent design ability, time-saving function, improved device compatibility, and ability to reposition design elements, which gives developers the flexibility they need. Therefore, it is an important tool in front-end development, especially when a high level of consistency is required.
2. Tell Us About The Disadvantages Of CSS
Despite the several advantages that this programming language offers to developers, it also has its fair share of disadvantages. First and most importantly, people have reported several cross-browser issues while using CSS, which is a significant disadvantage. Also, there are multiple levels of CSS which can lead to confusion, especially for non-developers or beginners. Knowing when and how to use CSS, CSS 2, and CSS 3 can be quite hectic.
3. Name The Main CSS Frameworks
There are four main CSS Frameworks that any front-end developer or software engineer should know. They include Bootstrap, the most common framework when creating mobile-first and responsive websites and foundations. It also comes with a responsive grid, CSS UI components, HTML and code snippets such as forms, buttons, typography, navigation, and an array of other UI elements. The other two are Ulkit, a light and modular front-end framework used to develop fast and powerful web interfaces, and Semantic UI powered by LESS, a CSS preprocessor, and jQuery. It is relatively more modern than its other counterparts.
4. Can You Explain What A CSS Preprocessor Is?
A CSS Preprocessor is an important tool developer, and software engineers use to crack the basic functioning of default vanilla CSS. It extends this basic functionality through its scripting language and therefore comes in handy when developers want to apply to challenge logical syntaxes such as functions, code nesting, inheritance, and variables. It supercharges the vanilla CSS, hence the name Preprocessor.
5. Explain What SASS Is
SASS is a common acronym in CSS, which stands for Syntactically Awesome Style Sheets. One can write it in different syntaxes through SCSS or SASS. However, there are three main differences between SASS and SCSS. Whereas the former is based on indentation, the latter is not. SASS also uses .sass extension while the latter.SCSS extension. Lastly, you can’t use curly brackets or semicolons with SASS, mandatory for SCSS. The latter therefore mirrors CSS.
6. Can You Tell Us What LESS And Stylus Are
Just like SASS, these two functions are equally important in CSS. LESS stands for Learner Stylesheets, which any programmer can easily add to any javascript project through NPM, LESS J’s file, or the extension .less. This syntax is similar to SCSS, save for a small exception. It is e @ when defining variables.
On the other hand, Stylus gives coders, programmers, or software engineers much-needed flexibility when writing syntax. It supports the native CSS and inputs semicolons, colons, and brackets. You don’t need @ or $ when defining variables.
7. Can You Differentiate Between Inline, Inline-Block, And Block?
These are three important elements in CSS that serve different important functions. A block element begins on a new line and occupies a whole width or row space. There are two main block elements namely <div> and <p> On the other hand, an online element doesn’t start in a new line but appear next to the nearest content and tags. There are four main inline elements namely: <a> , <span>, <omg> and <strong>.
Lastly, the inline-block elements bear a similarity to inline elements, just that they have padding, margins, width values, and set height options.
8. Differentiate Between Pseudo Elements And Classes
There are many elements and classes in CSS that play an important role in the overall functioning and operation of the language. The pseudo-elements allow developers to come up with items not usually found in a document tree. They include ::selection, ::first-letter, ::first-line, ::before and ::after. On the other hand, pseudo-classes are capable of selecting normal elements. However, some conditions must be met, such as hovering over the link by the user. These include :focus,:active, :hover, :visited and :link. It is also worth noting that the elements have double colons while the classes only have one.
9. How Do You Specify Units In CSS?
CSS offers users several ways of specifying units. These include em, px and pt, and percentage. Px stands for Pixelz and offers fine-grained control while maintaining alignment since 1px or multiple px normally looks sharp. On the other hand, Em maintains the relative size, allowing you to have responsive fonts. Pt stands for point and is usually used in print. Lastly, %(percentage) sets font sizes relative to that of the body. The font size of the body must be set to the right size.
10. What Do You Normally Use To Change The Font Face?
CSS has different properties used to perform various operations. We should use the font-family property to change the font face. It mainly specifies the font used on a specific DON element and can hold multiple font names, a feature christened ‘fallback mechanism’. The mechanism is important as it comes in handy when the browser does not support the fonts. Applying this property to a paragraph element will direct the browser to look for a given font and apply it or use a different one if the first is not installed. You can use as many fonts as you wish, provided you specify three.
11. Tell Us More About The Z-Index In CSS.
The Z-index is used with overlapping elements to define the vertical stacking in such elements. The overlap normally occurs during positioning. If you are wondering, the vertical stack order of the different elements is important as it sets ground rules for how elements display should occur in case of overlap. It has a default value of 0 and can either be positive or negative. It also has other values such as Auto, where the stack order is equal to the parent, initial where the default value is set to the property, inherit where the properties come from the parent, and number, which defines the stack order. Note that elements with lesser Z-index values are stacked lower than those with higher values.
12. Tell Us More About CSS Positioning
To answer this question accordingly, we will talk about absolute, fixed, static, sticky, and relative positions. An absolute position occurs when an element is placed at the exact intended place and generally set relative to an element’s parents. Fixed position occurs when an element is placed relative to a viewport or the browser window and stays in the same position since the viewport never changes. Static is the default position for every single page element. Use it to reset an element positioning that you didn’t initiate. Relative positioning, just like the name suggests, occurs when there is only a relative setting position on an element. You can use the Z-index on the element and ensure that all child elements are positioned within a block. Lastly, sticky positioning combines both fixed and relative positioning. The element is relatively positioned until it passes a threshold that unlocks fixed positioning.
13. What Do You Understand By DOM Reflow?
Reflow is a popular name in CSS, which refers to the recalculation of the positions and geometries of elements in a specific document. It is a web browser process that occurs to re-render the whole or part of a document. It mostly happens when one changes a CSS Style, animates or moves a DOM element, modifies page contents such as an input box’s text, and measures elements such as getComputedStyle and offsetHeight. It is, therefore, an entire concept in its entirety.
14. Can You Hide An Element Using CSS?
Yes. There are three different ways that CSS users can hide elements. They can use the display property- display: none, making the element unavailable for screen readers but non-existent in the display. The visibility property, visibility: hidden, comes in handy in hiding an element as it occupies its space. Even though it will be present in the DOM and available for screen reader users, it won’t be shown on the screen. Lastly, one can use the position property, position: absolute which makes an element available outside the screen.
15. Explain What Accessibility (a11y) Means In CSS
Accessibility refers to designing hardware and software combinations in a system that guarantees access to visually or hearing challenged people. It also covers other disabilities, such as limited dexterity. Such websites have text-to-speech capabilities to cater for the hearing impaired. The United States of America has a general rule that all public websites must be accessible to prevent discrimination. There is a 508 compliance guideline that has best practices that any web user cab employ to enhance accessibility. Guidelines are also included.
16. You Mentioned Padding and Margin At One Point During The Interview. Please Differentiate Them?
The margin properties allow us to create space around different elements and can be used to create borders defined at the exteriors. Some of the properties used to define the margin are margin-bottom, margin-right, margin-top, and margin-right. We also have auto where the browser automatically calculates the margin length where the value can be in px, cm, mm, pt and can be positive or negative values.
On the other hand, padding properties help generate the space around the content of an element and inside a defined border. Its sub-properties include padding-right, padding-bottom, padding-left, and padding-top.
17. Do You Know The Importance Of CSS Sprites?
CSS Sprites come in handy when combining several images into a single layer image since they represent icons found in the user interfaces. Some of the advantages of using sprites are a reduced number of HTTP requests, the ability to pre-download assets to help display ICO s or images upon different pseudo-states, and it empowers the browser to make separate calls and fetch single images where multiples exist. Sprites combine images into one unit, which you can access through a singular call.
19. Can You Fix Any Styling Issues Associated With A Browser?
There are several ways of fixing browser-specific issues in CSS, such as using an auto-prefix that automatically adds vendor prefixes in a given code, normalize.css or reset CSS methods, and separately writing browser-specific styles in different sheets meant to load only when using the given browser. This last method is closely linked with developers’ renowned server-side rendering technique. However, one can also easily avoid browser compatibility issues.
20. Mention Some Of The Ways Of Avoiding Browser Compatibility Issues
There are four main ways of avoiding issues surrounding browser compatibility. First, one can validate the HTML and CSS files for unavailable closing tags and missing syntax semicolons to counter the possibility of the old browser generating errors during code rendering. Testing on real devices and virtual elements will also come in handy. Other means include checking JavaScript library issues to ensure that the libraries are supported by the browsers and maintaining cross-browser compatibility in different layouts. The DOCTYPE tag keyword, which defines rules surrounding the code, can help avoid browser compatibility issues. However, all these must be done well.
21. What Would You Tell Someone Inquiring On How To Automatically Number Sectional Heading Values?
The best technique for automatic numbering of section or category heading values is observing the concept of CSS counters, which normally allow people to manipulate how content appears based on its location in a document. One must initialize the counter-rest value property, which is always 0 and can be changed into any desired value. The counter-increment property will, in turn, increase or decrease the counter’s value once post initialization is successful.
22. Tell Us About The Working Mechanism Of Absolute Positioning
Absolute positioning is one of the most important positioning mechanisms in CSS. It allows users to place any element in a location of their choice, It is usually exact, and the final position is often determined by the values to the bottom, right-left, and top. The element’s positioning is also relative to the nearest ancestor, whose absence forces the element to assume a position relative to the initial containing block. Lastly, the absolutely positioned element ceases to exist in the normal workflow of an HTML document.
23. What Do You Know About Progressive Rendering?
Progressive rendering refers to techniques that improve a webpage’s performance. They improve the perceived load time, thus rendering content as fast as possible. One commonly used progressive rendering technique is the lazy loading of images through APIs such as Observer, which ensures that one does not spend much time loading a webpage. You will easily notice an element’s entry viewpoint and choose what to do. You are free to begin loading the image immediately it enters the viewpoint.
24. What Is A Flexbox?
A Flexbox is a short-term for a flexible box. It came to the limelight in 2017 and aims to offer more flexibility in the CSS world. It serves different purposes, allowing people to efficiently handle layouts, distribute spaces among the different items in responsive conditions and align elements. The Flexbox is an enhanced tool that lets people change or manipulate an item’s dimensions, creating more space for more efficient use. It comes with a number of valuable properties.
25. Mention The Properties Of A Flexbox
A Flexbox has six properties serving different purposes. These include the flex-direction, which defines the directions for stacking different elements meant for flex. It has four different values: column, column-reverse, row, and row-reverse. The flex-wrap determines whether the different flex items should be wrapped or not. It has three possible values: wrap-reverse, wrap, and no wrap. The flex-flow combines both the flex-wrap properties and flex-direction in a single statement, while the justify-content property aligns the different flex items. It has the highest number of values, namely: space-around, space-between, flex-end, flex-stary, and center. Lastly, the align-items and content properties align flex items and flex lines, respectively.
Conclusion
We have covered some of the most asked questions in CSS interviews to give you an easy time to prepare for an upcoming assessment. Make sure that you understand the technical aspects of CSS to increase your chances of succeeding in your interview. We wish you all the best.
