Front End Developer Interview Questions

1. What is the difference between margin and padding in CSS?

Margin is the space outside an element, while padding is the space inside an element. Margin adds space between elements, whereas padding adds space within an element's boundary.

2. Explain the concept of responsive web design.

Responsive web design ensures that a website can adapt to different screen sizes and devices. It involves using flexible grids and layouts, media queries, and responsive images to create a seamless user experience.

3. Define HTML meta tags.

• Meta tags are passed as pairs of name/value.
• Meta tags can include data about encoding, document title, character description, etc,
• Meta tags fit inside the HTML page’s head tag.
• Meta tags are not displayed on the page but it is to be shown on the browser.

4. Differentiate between div and span?

5. How browsers render the UI?

The primary responsibility of the rendering engine is to highlight the requested page on the browser’s screen. Rendering engines can show XML and HTML images and documents. If you’re utilising additional plugins, the engines can also exhibit various documents like PDF.

• Receives the requested document: The contents of the requested document is obtained by the rendering engine from HTML’s networking layer.
• Construct the DOM tree: Parsed the HTML to the parsed tree and then set up the DOM tree, making use of it.
• Construct the CSSOM: CSSOM stands for CSS Object Model. Post the construction of the DOM tree, it identifies a link tag in the head section, which references the external style.css CSS style sheet. So, it parsed the CSS file in CSSOM tree, something which the Browser can comprehend as the DOM tree.
• Construct the Render tree: Utilise the HTML DOM tree coupled with the styling data of the CSSOM tree to set up a render tree. Render tree is the graphical depiction of the HTML, with the corresponding CSS. This tree enables painting the contents in their right order. Every node in the Render Tree is regarded as a renderer. The Render tree looks like this:
• Layout: When the renderer is developed and incorporated into the tree, it does not have a size or position. Computing these values is defined as layout. We use the coordinates system to position the element, such as the position of the root renderer is 0,0. The layout continues recursively via a part of the entire renderer hierarchy, calculating geometric info for every renderer that needs it. Beginning the layout process implies allowing every node the exact coordinates where it should show up on the screen.
• Painting of the Render Tree: The renderer tree is traversed in this stage and the renderer’s paint() method is hailed to exhibit the content on the screen. For good UX, the rendering engine will aim to exhibit the contents on the screen as soon as possible. It will not stand by until all the HTML is parsed to develop and layout the render tree.

6. What is a Grid system in CSS?

CSS splits the page into grids and utilizes those grids to handle the HTML content. Utilizing the Grids, CSS can stack and highlight various elements in different parts of the grids.

7. Describe the distinction between Class and Prototypal inheritance in Javascript?

From most other programming languages, Inheritance in JavaScript is different. JavaScript's object system is prototype-based, not class-based. Objects in JavaScript are just a set of value pairs and a name (key). Talking about inheritance, JavaScript just has one construct: objects. Each object has a private property that includes a link to another object named its prototype.

8. Explain user-centered design?

An iterative design procedure, User-centred design lets the designers focus on the clients and their needs in every design process phase. The user-centered design calls for linking users in the design process via a variability of design and research techniques to make usable and highly accessible products. User-centered design demands that designers should utilize a combination of generative (such as brainstorming) and investigative (interviews and surveys) methods and instruments to create an understanding of user requirements.

9. What is ClickJacking?

ClickJacking is a security attack where the user is fooled to click on something while they assume they are clicking another thing. The attack mostly happens by the HTML frames. ClickJacking is also regarded as the user interface redressing. It lets the user think that they are utilising a normal UI in the web page, but in actuality, there is an unseen UI in control; you can think of it as the user interface being redressed. When users click on one thing, assuming it to be secure and safe, the hidden UI executes another action.

10. Tell me when and why should I make use of Webpack?

While creating a complicated front-end application with tons of non-code static possessions, for instance, CSS, fonts, images, etc, then, of course, you should make use of Webpack since it has a lot of amazing benefits.

If you have a small application that doesn't have a lot of static resources and you only have to create one file of JavaScript to help the customers, then Webpack should be more overhead than needed.

11. Mention three ways to decrease page load time?

There are numerous things accountable for lowering page load time. Let us look at the three best ways to reduce its loading time:

• Image Optimization: It is always advised to scale your videos and pictures before uploading them to a page.
• Browser Cache: The utilization of cache will boost speed for pages that you have visited already.
• Optimize and compress content: Compressing the content of a website decreases the load time of a page to a great extent.
• StyleSheet Reference on Top: Setting stylesheet reference to the header of a doc allows your page to load quickly.

12. What is Progressive Rendering?

Progressive rendering is a process that is utilized generally to boost the web page's rendering content process. Now the rendering process is utilized in modern web development to enhance the mobile data uses of the user, async HTML fragments, prioritizing visible content, and lazy loading of images.

13. In an image tag, what is the benefit of the srcset attribute?

srcset is utilized when we wish to generate several resolutions of the exact image on several devices. This improves the UI. The browser will display low resolution on low-end devices, and high resolution of an image on high-end devices.

Example:

<img srcset="picture_low.jpg 480w,             picture_high.jpg 800w"     sizes="(max-width: 600px) 480px,            800px"     src="/blog/picture_high.jpg"     alt="Elva dressed as a fairy">

14. Mention the difference between MySQL and MongoDB?

• MySQL: It is a Relational Database Management System (RDBMS), which makes use of SQL as a standard language to handle its database. Like different relational database management systems, MySQL makes use of a table-like structure to stow data.
• MongoDB: MongoDB is a NoSQL database that utilizes the JSON-like structure to stow data elements. To modify and access data in MongoDB, the programmer ought to make use of the MongoDB Query Language (MQL).

15. What do you know about the CSS image sprites and why it is utilized?

CSS image sprites assist to render numerous images in a single line image. In a nutshell, the CSS sprites merge numerous photos into a single large image. If a web page comprises different images, then it would raise its loading time as for every image the browser has to send a distinct HTTP request, but with the help of sprites, we have a single image to request.

16. Suggest some ways on how to fix the browser-specific styling issue?

• We can make a distinctive stylesheet for various browsers making use of server-side rendering.
• Another method is utilizing a library such as Bootstrap, which already has the code to manage the browser-specific styling issue.
• Reset or Normalize CSS can also be utilized. Multiple 3rd party plugins equip libraries for browser styling issues.

17. Mention the pitfalls for using a CSS Preprocessor like Sass?

• An extra tool for the preprocessor is required.
• Preprocessor files can not be performed directly on the browser.
• Slow re-compilation of the preprocessor.
• For the preprocessor, you ought to know extra tools, which improve the learning curve of CSS.

18. Suggest how can we optimize our front-end page.

• The consumption of resources can be reduced by the pages by enhancing the server response.
• Utilize JavaScript and External CSS instead of internal or in-line.
• Utilize the framework to ensure the front-end becomes more responsive to different devices.
• Open-source libraries can be used to manage the browser-specific styling issue.
• Make use of progressive loading like Lazy Loading to enhance the rendering of heavy elements, like videos and images.
• Connect the style sheet in the header and script at the top of the HTML's body tag.
• Utilize browser storage to keep user-specific private data.

19. What is the difference between attribute and property?

Attributes are an element of an HTML document while properties are a part of the Document Object Model (DOM).

Example: <input type="text" value="Tech">

Here, value and type are the attributes of HTML, but when the statement is read by the browser and parses this code it will make a DOM with different properties, like accept, autofocus, accessKey, baseURI, checked, childElementCount, align, alt, childNodes, children, classList, className, attributes, and clientHeight.

Example:

var data = document.querySelector(input);  // here we created a document object of input tagconsole.log(input.getAttribute('value')); // tech  // getting the attribute valueconsole.log(input.value); // tech   // getting the property of the input object

20. State the difference between == and ===?

 == denotes abstract equality operator, and it inspects if two values are equal or not apart from their data types. Automatically, it transforms the type of both the operands and compares them.

Example: 

1=='1';    //true1==1;   // true

=== denotes identity equality operator, and it inspects the values of both the operands and their data type. The outcome of the operation will be true considering both the operands are equal and have the same data type, or else it returns false.

Example: 

1===1   //true1==='1'   // false

21. Why do we utilize the “use strict”; statement?

The ‘use strict’ statement sets a few restrictions in the script. Typically, it is utilized to facilitate the strict mode of the script, making sure there could be no loose coupling like undeclared variables.

22. How do I prepare for a front-end developer interview?

When you're preparing for your Front-end developer interview, try to code most of your layout without taking a glance at the result till the end. If CSS, HTMLare the most important aspect of front-end development, then JavaScript tops the list of important skills to own. Organisations will spend a lot of time during your interview to test your understanding of Javascript.

23. Why should we hire you as frontend developer?

• Freshers:  While interviewing for front-end developer jobs for freshers you can come across this question. The best answer would be, " I have just begun my career, and do not have practical achievements, but I wish to explore and experience my potential by giving the best services to the company. It will be my privilege to work with your organization."
• Experienced: The best answer would be, “You should hire me for the role of front-end developer owing to my proven ability to create effective front-end user interfaces in line with contemporary best practices. I have experience working with JavaScript, along with the React framework, to create front-end applications.”

24. What is the most challenging work you have ever done as a front-end developer?

The biggest challenges faced as a front-end developer are:

• Make sure each UI element like button, link navigation,  works as planned despite the user having JavaScript or cookies disabled.
• Make sure everything looks similar across all browsers.
• HTML tables.
• Debugging JavaScript code.

25. How much do front end developers get paid?

As per the payscale, freshes, front-end developer gets an average of ₹305,498 per annum. An intermediate developer's salary is ₹452,073 on average. A senior developer can earn an average of ₹806,231.

26. Which language is best for front end development?

The languages best for front-end development are HyperText Markup Language (HTML), Cascading Style Sheets (CSS), JavaScript, React, Angular, Vue.

27. Code Snippet: Creating a Simple HTML Page

    
      <!DOCTYPE html>
      <html lang="en">
      <head>
          <meta charset="UTF-8">
          <meta content="IE=edge" http-equiv="X-UA-Compatible">
          <meta content="width=device-width, initial-scale=1.0" name="viewport">
          <title>Your Page Title</title>
      </head>
      <body>
          <h1>Hello, World!</h1>
      </body>
      </html>
    

28. Online Resources:

• MDN Web Docs - CSS
• W3Schools - HTML Tutorial