Front End Developer Interview Questions

Front End Developer Interview Questions for Experienced

29. How to optimize a website's accessibility and SEO?

We can optimize a website’s accessibility using the following ways:

• Use proper HTML structure and semantics. It makes the website easy to understand for both users and assistive technologies.
   
• Use descriptive and concise text for links, images, and other web page elements.
   
• Provide alternative text(alt text) descriptions for images and other non-text content.
   
• Use good color contrast to make content easily visible.
   
• Make sure the website is keyboard navigable.
   

We can optimize a website’s SEO(Search Engine Optimization) in the following ways:

• Use proper HTML structure and semantics. It makes the website easy to understand for search engines.
   
• Include descriptive and concise meta titles and descriptions for each web page.
   
• Use relevant and descriptive headings to break up content.
   
• Make sure that the website is mobile-friendly and it loads quickly.
   
• Use relevant keywords in page content, but avoid keyword stuffing.
   
• Include internal and external links to relevant content.
   
• Use alt tags and proper file names for images.

30. What do you understand by version control tools like Git as a front-end developer?

As a front-end developer, version control tools like Git help to manage changes. It provides features for collaboration with others in a project. Git allows developers to keep track of changes made to code over time. We can revert to previous versions of code and collaborate with others on the same codebase.

Some common use cases for version control with Git in front-end development are mentioned below:

• Keeping track of changes to HTML, CSS, and JavaScript files.
   
• Collaborating with other developers on a codebase.
   
• Branching and merging code changes for different features or experiments in a project.
   
• Creating backups of code.
   
• Identifying who made changes to the code and when.
   
• Roll back to a previous version of the code if necessary.
   
• Managing code releases and deployments.

31. How to build or integrate an API with front-end applications?

To build or integrate an API with front-end applications, you can follow these steps:

1. Determine the purpose and requirements of the API that you want to build or integrate.
    
2. Choose an appropriate API technology, such as REST or GraphQL.
    
3. Design the API, which has endpoints, data structures, and expected responses.
    
4. Implement the API using a server-side programming language, such as Node.js, Python, or Ruby.
    
5. Test the API using tools like Postman.
    
6. Make secure API by implementing authentication and authorization mechanisms.
    
7. Document the API, including usage instructions and examples of responses.
    
8. Integrate the API with your front-end application by requesting API endpoints using technologies like JavaScript or AJAX(Asynchronous JavaScript And XML).
    
9. Handle API responses, including error handling and data parsing.
    
10. Test the integration and check whether the data transfers properly between the API and the front-end application.

32. Explain hoisting in JavaScript.

Hoisting is a behavior in JavaScript in which the variables and function declarations are moved to the top of their respective scopes(global or local) during the compilation phase before any code is executed.

The variable and function can be used before they are declared as long as they are declared in the same scope. For example

// Output: undefined
console.log(val);
var val = 25;

In the above code, we have declared a variable val and assigned a value of 25 after it has been referenced in the console.log statement. However, since the declaration is hoisted to the top of the scope, the output of console.log(val) will be undefined.

Similarly, function declarations are also hoisted to the top of their respective scopes. For example,

// Output: "Hello, Ninjas!"
ninjas(); 
function ninjas() {
  console.log("Hello, Ninjas!");
}

In the above code, the ninjas function is declared and defined after it has been called. Since the function declaration is hoisted to the top of the scope, the output of ninjas() will be "Hello, Ninjas!".

It's important to remember that only the declarations are hoisted, not the assignments. So, in the case of variables declared with let and const, they will not be accessible until they are assigned a value.

33. Explain the differences between == and === in JavaScript.

In JavaScript, both == and === are used for comparison, but they have different behaviors. Here are some of the differences between them.

==	===
It is a loose equality operator, which means it will perform type conversion if the operands have different types.	It is also known as the strict equality operator, which means it does not perform type conversion.
It only returns true if the operands have the same value. It will not check their types.	It only returns true if the operands are of the same type and have the same value.
It is slower than === because it needs to perform type conversion.	It is faster than == because it does not need to perform type conversion.
It is not much safer than ===.	It is safer than ==.

34. What do you mean by cookies in JavaScript?

In JavaScript, cookies are small text files. These are stored on a user's computer by a website. They are used to store user-specific information, such as login credentials, shopping cart items, and preferences.

Cookies are created and accessed using the document.cookie property. Here's an example of setting a cookie with JavaScript:

document.cookie = "username=Coding ninjas; 
expires=Sat, 18 Feb 2023 23:59:59 GMT";

In the above code, a cookie named username is created with the value of Coding ninjas and an expiration date of February 18, 2023.

It's important to remember that cookies can be a potential security risk if they contain sensitive information. For this reason, it's recommended to use cookies only for non-sensitive data. We should use proper security measures, such as encryption and HTTP-only cookies, for sensitive data.

35. What is Bootstrap, and what are its benefits?

In front-end web development, "Bootstrap" is a popular open-source CSS framework. It provides pre-designed HTML, CSS, and JavaScript components for building responsive and mobile-first web applications. The benefits of using Bootstrap are mentioned below:

• Saves time and effort by providing ready-to-use UI(User Interface) components and design templates.
   
• It helps to ensure cross-browser compatibility. It provides responsiveness to web pages on different devices.
   
• It provides a consistent and visually appealing design for web applications.
   
• It offers customizable and extensible components which are used in advanced front-end development.
   
• It has a large community of developers and resources that are available for support and learning.

36. What do you understand by closure in JavaScript?

In JavaScript, closure combines a function and the lexical environment. The lexical environment consists of any local variables that were in scope when the closure was created.

Closures are created whenever a function is defined inside another function. The inner function references a variable from the outer function's scope. Here's an example:

function outerFun() {
  const val = 20;
  function innerFun() {
    console.log(val);
  }
  return innerFun;
}
const innerVal = outerFun();
console.log("Returned value is");
innerVal(); 

We will see the output as follows:

Returned value is
20

In the above code, the innerFun function is defined inside the outerFun function. innerFun() references the val variable from the outerFun function's scope. When the outer function is called, it returns the innerFun function, which is then assigned to the innerFunc variable. When innerVal is called, it still has access to the val variable, even though the outerFun function has already been completed.

37. How MongoDB and MySQL are different from each other?

The difference between MongoDB and MySQL is mentioned in the table below.

MongoDB	MySQL
It is an open-source database which is developed by MongoDB, Inc. It stores data in JSON(JavaScript Object Notation) format that can vary in structure. It is a NoSQL database.	It is an open-source relational database management system (RDBMS). It is developed, distributed, and supported by Oracle Corporation.
Each individual record is stored as a document.	Each individual record is stored as a row in a table.
Documents belonging to a particular class or group are stored in a collection.	A table stores rows (records) of a similar type.
It was designed with high availability and scalability. It includes an out-of-the-box replication and sharding.	It does not allow efficient replication and sharding. With MySQL, we can access associated data using joins which helps to minimize duplication.

Beginner Level Front End Interview Questions

1. What do you understand by DOCTYPE?

Answer: DOCTYPE stands for Document Type and is directly associated with Document Type Definition(DTD). All HTML documents must start with a <!DOCTYPE> declaration.The function of DOCTYPE is to tell the browser about the version of the HTML specification the document represents.

<!DOCTYPE html>
<html>
<head>
<title>Title</title>
</head>

<body>
Hello everyone!
</body>

</html>

2. What is the difference between === and ==?

Answer: The  == checks only the value, whereas === checks for both the value and its data type. For example, (‘5’==5) will be true, but (‘5’===5) will be false.   

3. What is the difference between undefined and null?

Answer: The variable would be undefined when we declare a variable and do not give any value. If we want to have a variable with no value, we can assign a null value. Undefined represents no value, whereas null is a value.

var a;
var b= null;

 

Here a is undefined, and b is null.

4. What is NaN?

Answer: Nan (Not a Number) is the property of the global object, or it is a variable in the global scope. If some input parameters in a floating-point operation cause the operation to produce an undefined result, "Nan" is produced. 

For example, “Coding”-5 is NaN.

50. What are the disadvantages of ‘use strict’;.

Answer:  The disadvantages of ‘use strict’ are as follows:

• Concatenation of scripts written in various strict modes may result in problems.
• We lose some Javascript features if we use ‘use strict.’
• We would not be able to access .arguments and .caller methods.

6. What is the type coercion in JS?

Answer: Type coercion is the process of converting a value from one type to another. Using this method, we can convert a string to a number, or an object to Boolean, and so on. For example:

var a= 11;
var b = String(a);
typeof(a)
"number"
typeof(b)
"string"

 

There are two types of Coercion:

• Implicit Coercion
• Explicit Coercion

 

Implicit Coercion: In this type of coercion, JS changes the data type of a variable.

For example:

var x= 20;
var y= x+'21'   // y will be "2021"

 

Here, JS changes the value of x 20 into string ‘20’ and concatenates it with ‘21.’

Explicit Coercion: In this type of coercion, the developer changes the data type of a variable using in-built functions, such as Number(), String(), and Boolean(). For example:

var x = "11"
var y = Number( x );   // 11

7. What are meta tags in HTML documents?

Answer: Meta tags are written inside the <head> tag. They are used to give the metadata of the HTML document. The meta tag is used to specify the document specification, such as page author name, document page description, page keywords, page character set, page language, and page viewport setting.

<head>
  <meta charset="UTF-8"> 

  // Description of your web page
  <meta name="description" content="Top 50 Interview Questions">

  // Keywords for search engines
  <meta name="keywords" content="HTML, CSS, JavaScript"> 

  // The author of a page
  <meta name="author" content="Coding Ninjas">

  // Set the viewport to enhance the look of the website on all devices.
  <meta name="viewport" content="width=device-width, initial-scale=1.5">
</head>

8. What is Variable Scope in JS?

Answer: The scope of the variable determines the variable accessibility in a particular function.

There are two types of Variable Scopes in javascript:

• Local Scope
• Global Scope

 

 Local Scope: In this scope, the visibility or accessibility of a variable is limited to a specific function. Let’s understand it with an example:

function ninjas() {
  var course = "Web Development";  // course is limited to ninjas because it is a local variable
}
function dev()
{
//dev cannot access the course variable because it is local to the ninjas() function
}

 

Global Scope: We define a variable outside the function accessible for all other functions in this scope. This sets the variable scope global. Let’s understand it with an example:

var course = "Web Development";  // It is a global variable
function ninjas() {
var getninjas = course;
}
function dev()
{
var getninjas = course;
}

9. What is Node.js?

Answer: Node.js is a cross-platform, non-blocking I/O and open-source runtime environment capable of building highly scalable server-side applications using Javascript.

10. What is npm?

Answer: The npm (node package manager) is a package manager tool for node.js. NPM provides an online repository for open-source Node.js projects and a command-line utility for managing and installing different versions of packages.

11. What is Flexbox?

Answer: Flexbox is a layout system for CSS, which W3 specifies. It allows us to position elements inside a container even if the container size is dynamic.

Intermediate Level Front End Interview Questions

12. What do you understand about IIFE?

Answer: IIFE stands for Immediately-Invoked Function Expression. The functions that are executed as soon as they are mounted are called IIFEs.

x=10;
(function () { alert(x)})();

 

When we look at the syntax, we see two pairs of closed parentheses. The first contains the logic to be executed, and the second is what we use when we call a function. The second parenthesis tells the compiler that the function expression must be executed immediately.

13. What is the callback function in JS?

Answer: We can pass one function as an argument to another function. The function that is being passed as a parameter to another function is called a callback function. The advantage of using a callback function is that we can execute another function call after waiting for the result of a previous function call. 

For example:

function helloNinjas(call_back)
    {
        call_back();
    }

14. What is React.js?

Answer: React.js is a JavaScript library used to build user interfaces for SPAs (single-page web applications). For creating user interfaces, React is a declarative, efficient, and adaptable JavaScript library.

15. Why is it preferred to use external JS and CSS than in-line?

Answer: The in-line JS and CSS slow down the code execution process and increase HTML document size. Although no browser saves the entire HTML file as cached storage, the external JS and CSS files can be cached by the user browser.

16. What does the ‘this’ keyword do in JS?

Answer: The ‘this’ is used to refer to the object it belongs to. Every javascript function has a reference to its current execution context, called this, while it is running. The execution context specifies how the function is invoked. This is similar to the concept of dynamic binding used in other high-level programming languages. 

Let us understand it with an example:

const year = {
  prop: 2021,
  func: function() {
    return this.prop;
  },
};

console.log(year.func());
// expected output: 2021

17. What is SQL injection?

Answer: In SQL injection, the user enters malicious code into the input forms to hack the webpage’s SQL database. It is the most powerful and widely used hacking method. Additionally, using the SQL injection technique, a badly designed website can be easily attacked and destroyed.

18. What are the elements of the CSS Box Model?

Answer: There are four elements in the CSS box model:

• Content: It refers to the main content and the text of the web page.
• Padding: It refers to the area that covers the content.
• Border: It refers to the outer layer of padding.
• Margin: It refers to the area outside the border.

19. What is Sass?

Answer: Sass stands for Syntactically Awesome Stylesheet. It is a CSS Preprocessor that adds features like variables, nested rules, and in-line imports, which help us to optimize our CSS code. It's fully compatible with all CSS versions. Sass cuts down on CSS repetition and thus saves time. Although the syntax of Sass is very similar to that of CSS, Sass files cannot be executed directly by the browser. 

Also read, Power Apps Interview Questions

20. Differentiate between a cookie, local storage and session storage?

Answer: The table below shows some of the key differences between a cookie, local storage and session storage.

Parameters	Cookie	Local Storage	Session Storage
Accessibility	Any window can access	Any window can access	The same tab can access
Persistent across browser sessions	It depends on whether expiration is set.	Yes	No
Sent back to the server	Cookies are sent back automatically via the cookie header.	No	No
Storage Capacity	4kb	5MB	5MB
Expiry	It has no expiration time but can be destroyed manually.	No expire time	It expires automatically after the session ends.

 

21. What do you mean by Progressive Rendering?

Answer: Progressive rendering is a technique for speeding up the content rendering process on a website. In modern web development, the rendering process is now used to optimize the user's mobile data usage, prioritize visible content, lazy loading of images, and async HTML fragments.

22. Why do we use the srcset attribute in an image tag?

Answer: Srcset is a new attribute that specifies different image types for various screen sizes, orientations, and display types. The usage is straightforward; simply provide a large number of different images separated by a comma. For example: 

<img srcset="picture_low.jpg 480w,
            picture_high.jpg 800w"
    sizes="(max-width: 500px) 400px,
            700px"
    src="picture_high.jpg"
    alt="Welcome to Coding Ninjas">

23. What do you mean by templating language?

Answer: The HTML templating language is a placeholder that allows a user to insert data into an HTML document. Many templating languages exist, and they frequently work with a back-end language or framework.

Jinja, for example, is a popular templating language that works with Django and Flask, both of which are Python frameworks. Slim is a templating language used by Ruby and Rails.

24. What is a CSS float?

Answer: CSS float is the property of positioning. CSS float specifies how an element should float in the viewport based on the size of the device.

25. What do you mean by semantic HTML?

Answer: Using the most appropriate tag for the task at hand is what semantic HTML is all about. It means that instead of just using div and span, you should use meaningful elements like form, article, and table.

26. What is the difference between DIV and SPAN in HTML?

Answer: A span element is in-line and is usually used for a small chunk of HTML inside a line, such as inside a paragraph. A div or division element, on the other hand, is block-inline, meaning it has a line break before and after it and is used to group larger chunks of code. Let us see an example:

<div id="HTML">
This is <span class="Coding Ninjas">Web dev</span>
</div>

27. What is a CSS Grid system?

Answer: The CSS grid is a grid-based system that makes designing a web page easier by using rows and columns without any floats or positioning.

Syntax:

.grid_container{
    display:grid;
}

28. What are the limitations of using a CSS Preprocessor like Sass?

Answer: The drawbacks of using a CSS Preprocessor like Sass are as follows:

• It is not possible to run preprocessor files directly in the browser.
• We require an additional tool for the preprocessor.
• The preprocessor's recompilation is slow.
• The preprocessor demands the need to learn extra tools for use.

29. What is the main difference between visibility: hidden and display: none?

Answer: The visibility: hidden hides the element, but it still takes up space in the layout. The display: none removes the element from the document entirely. Even though the HTML for it is still in the source code, it takes up no space. 

30. What is the role of W3C?

Answer: W3C stands for World Wide Web Consortium. The World Wide Web Consortium (W3C) is an organization that regulates and develops web standards to ensure cross-platform compatibility. The W3C is also in charge of HTML and CSS development and maintenance.

Advanced Level Front End Interview Questions

31. What are CSS image sprites, and why is it used?

Answer: CSS image sprites is an image that is made up of a number of different images that have been stitched together to form a single image. It is used to speed up page loading by using only one image. It cuts down the amount of bandwidth required to load multiple images. As a result, less data is consumed.

Image sprites are used to design a graphic social media bar or navigation bar to make it more efficient and appealing. It's just an HTML and CSS method for putting images and creating web pages more efficiently.

32. Differentiate between class and id attributes?

Answer: The id-attribute is an abbreviation for the identifier. It gives the element a name. The name must be unique and should not be used anywhere in the document. It is used when you want to be able to identify a specific element.

Classes are used to give your element some general properties. This means that your document can have multiple elements with the same class name. This is typically used for things like links and images when you want a lot of them to look the same. 

For example:

<div id="logo">
<h1>Coding Ninjas</h1>
<p class="intro">Just prepare these interview questions</p>
<p class="intro">All the best</p>
</div>

33. Suggest a method on how we can fix the browser-specific styling issue?

Answer: Methods to fix the browser-specific styling issue are as follows:

• We can use Reset or Normalize CSS.
• Many third-party plugins include libraries to help with browser styling.
• Using server-side rendering, we can create a unique stylesheet for each browser.
• Another option is to use a library such as Bootstrap, which already has the code to deal with the browser-specific styling problem.

 34. What is a ternary expression, and why is it called ternary?

Answer: Ternary expression is an alternative, or we can say a shortcut for the if-else statement. There are three arguments of the ternary operator:

• The first argument is for a comparison.
• The second is the outcome of a true comparison.
• The third is the outcome of a false comparison.

Syntax:

condition_check ? truth_block : false_block

Example:

var ninjas = true;
var success = ninjas ? 2021 : null;// 2021 will be printed.

 35. What is the difference between .call and .apply?

Answer: The only difference between call() and apply() methods is that apply() takes an array of arguments, whereas call() takes arguments separated by commas. 

For example:

function add(a, b) {
  return a + b;
}
console.log(add.call(null, 6, 5));  // 30
console.log(add.apply(null, [6, 5]));  // 30

36. What is event delegation?

Answer: Event delegation is a pattern for efficiently handling events. Rather than adding an event listener to every similar element, we can add an event listener to a parent element and use the .target property of the event object to call an event on a specific target.

 37. What is hoisting?

Answer: Variable and function names can be used before declaring them in JavaScript. The JavaScript compiler moves all variable and function declarations to the top of the code to avoid errors. This is referred to as hoisting. 

For example:

a = 1;
alert('a = ' + a); // for displaying a = 1
var a;

 

 

The above diagram explains the hoisting in the code.

38. What is the difference between native and host objects?

Answer: The differences between native and host objects are given below:

Native Objects	Host Objects
Host Objects are created by the environment and are environment-specific.	A Native Object is created by the developer using predefined classes of JavaScript.
Host objects are objects that the browser (or another runtime environment like Node) provides.	Native objects are objects that adhere to the specs, i.e. "standard objects".
The ECMAScript specifications define native objects in JavaScript.	These objects are provided by the runtime environment, such as the browser and Node.js.
Examples of native objects are RegExp, Object, String, Math, and Function	Examples of host objects are XMLHTTPRequest and  Windows.

39. What is AJAX?

Answer: AJAX stands for Asynchronous Javascript and XML. It is not a programming language, but it is used to load and communicate data between the client browser and the server after the page has been fully loaded. It is used to communicate with the server without having to refresh the page, resulting in a better user experience and performance.

40. Give some disadvantages of using AJAX.

Answer: The disadvantages of using AJAX are:

1. Bookmarking dynamic web pages became difficult.
2. AJAX would not work if the user disabled JavaScript in their browser.
3. As JavaScript is continuously executed in the browser, AJAX is incompatible with low-end mobile devices.
4. Ajax makes it tough to debug your website.
5. It increases the size of the code.
6.  It exposes websites to potential security threats.

 41. State the major HTTP requests.

Answer: The major HTTP requests are as follows:

HTTP Requests	Description
DELETE	It is used to delete data from the server. When we want to delete our account, we can use the DELETE HTTP request.
GET	When we want to get data from the server, we send a GET request. It's the most frequently used HTTP request type.
PATCH	It is used to update a specific area of our data. For example, we can use the PATCH request to alter our name or any other relevant information about our account.
POST	Data is sent from the user to the server using the POST request. Web forms can be used to make POST requests. POST requests are frequently used to create data into databases. When we establish a new account on a website, we usually use the POST request.
PUT	It's used to update the server's existing data. For example, we make the PUT request to update our entire account on a web page.
OPTIONS	It enables us to achieve information about the requests that the server has accepted.

42. What is Polymorphism?

Answer: Polymorphism refers to the ability to take multiple forms. It is one of the most important properties of object-oriented programming. The action of the same operators on different objects is referred to as polymorphism. 

For example, the + operator performs a concatenation operation on two strings. It also performs an addition operation on two numbers.

"x"+"y"; //"xy"
2000+21; //2021

43. What does the KISS principle state?

Answer: KISS stands for “Keep It Simple, Stupid.” It means that you should keep your design simple rather than complex. The US Navy stated this principle in 1960, and many industries, particularly web design, have adopted it.

44. What is stringify?

Answer: To make a JSON string out of a javascript object or value, we use the JSON.stringify() method. When developing a JavaScript application, it is often necessary to serialize data to strings to store it in a database or send it to an API or web server. With the help of the JSON.stringify() method, we can easily convert an object to a string.

Syntax:

JSON.stringify(value, replacer, space)

For example:

var data = { ID:1, First_name: "Coding", Second_name: "Ninjas" };
var send_data = JSON.stringify(data);

45. What are the differences between MySQL and MongoDB?

Answer: The difference between MySQL and MongoDB are as follows:

MySQL	MongoDB
MySQL is an open-source relational database management system (RDBMS). Oracle Corporation is responsible for its development, distribution, and support.	MongoDB is a database that was created as an open-source project by MongoDB, Inc.
Individual records are stored as 'rows' in a table in MySQL.	Individual records are stored as 'documents' in MongoDB.
MySQL uses Structured Query Language (SQL) for database access. It is not possible to alter the schema. Only the inputs that follow the given schema are entered.	MongoDB is a type of database known as a NoSQL database. It means that not only a pre-defined structure for incoming data can be defined and followed, but the different documents in a collection can also have different structures if necessary.
Although the MySQL concept does not allow for efficient replication, joins can be used to access related data, reducing duplication.	MongoDB was built with high scalability and availability in mind and included replication out of the box.

46. What is the Anonymous function in JS?

Answer: We usually define the function name when we define it in user-defined functions, but we don't define the function name in anonymous functions. We use a variable and the assignment operator to store the function as an object, and then we can use that variable to call the function. 

For example:

var mul = function(a,b){ console.log(a*b)}
mul(6,5); //30

47. What is the main difference between JavaScript and jQuery?

Answer: The main difference between JavaScript and jQuery are given below:

JavaScript	JQuery
JavaScript is a programming language.	JQuery is a library written in JavaScript
JavaScript offers endless possibilities to make web pages more interactive and dynamic	JQuery has a limited scope.
JavaScript was created as an integral element of the web development process.	JQuery was developed to make web development through JavaScript easier and faster.
JavaScript is an essential component in client-side web development. Also, its use in server-side applications is experiencing an exponential rise.	JQuery is only used for client-side development.
JavaScript underperforms when it comes to complex logic.	JQuery is the ideal alternative for complex logic.

Must Read Web Developer Interview Questions

48. Why should we use jQuery?

Answer: We should use jQuery because of the following reasons:

• It is cross-browser compatible.
• It has a low learning curve and can be expanded easily.
• AJAX compatibility is included.
• There are a lot of built-in methods and properties.
• It also includes many ways for modifying CSS, which come in handy when working with animation.
• It has event detection and handling, just like JavaScript.
• It has a wide range of third-party plugins to meet any need.
• It has a simple interface for manipulating and traversing the DOM.

49. Why do we use the “use strict” statement?

Answer: Strict Mode is a new feature in ECMAScript 5 that lets us put a function in a “strict” operating context. It's used to apply the script's strict mode, preventing loose coupling, such as undeclared variables. It makes the code clean and reduces the number of problems and exceptions caused by hoisting. 

Let us understand the use strict with an example:

"use strict";
a= 2021; // it will give an error because a is not declared.

50. What is a marquee?

Answer: In HTML, the <marquee> tag is used to make scrolling text or images on a webpage. It scrolls vertically top to bottom or bottom to top or horizontally left to right or right to left.

For example: In the example below the text CODING NINJAS will scroll in the upper direction.

<marquee width="60%" direction="up" height="100px">
CODING NINJAS
</marquee>

51. What do you mean by the SOLID principle in front-end development?

The SOLID principle is a set of five design principles in object-oriented programming. It can be applied to front-end development to improve the quality, maintainability, and scalability of code. The five principles are as follows:

1. Single Responsibility Principle (SRP): A component or module should have only one reason to change.
    
2. Open-Closed Principle (OCP): A component or module should be open for extension but closed for modification.
    
3. Liskov Substitution Principle (LSP): Subtypes should be substitutable for their base types.
    
4. Interface Segregation Principle (ISP): Clients should not be forced to depend on methods they do not use.
    
5. Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules. Both should depend on abstractions

Frequently Asked Questions

What to expect in a front-end interview?

In a front-end interview, one should be prepared with the knowledge about the tech stack being used, such as HTML, CSS, and JavaScript. One should know about the concepts and be prepared to discuss all the components with various tools, frameworks, and programming languages.

Why do you want to be a front-end developer interview answer?

The answer can include all the points which excite you about being a front-end developer. Here is a sample answer, “I have always been passionate about web development as I am motivated by the new innovations in web technologies which makes me passionate about creating visually appealing and interactive applications.”

How do I prepare for a front-end technical interview?

To prepare for a front-end technical interview, firstly, one should be well-versed which the fundamental concepts of HTML, CSS, and Javascript. In the front-end knowledge part, you must explain your projects in depth and be prepared for recreating a design that an interviewer may ask. 

Conclusion

In this article, we have discussed top frontend developer interview questions and answers. We have discussed interview questions in three categories: beginner, intermediate, and advanced. You can check out our other interview questions blogs:

• Talend Interview Questions
   
• ETL Testing Interview Questions
   
• Team Leader Interview Questions
   

We hope this article helped you in learning about front-end developer interview questions. You can read more such articles on our platform, Coding Ninjas Studio. You will find articles on almost every topic on our platform. Also, you can practice coding questions at Coding Ninjas to crack good product-based companies. For interview preparations, you can read the Interview Experiences of popular companies. 

Happy Learning!!