Front End Web Development: Get Started

Front End Web Development Interview Questions & Answers

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1) What are the technical and additional skills that are needed to be a front-end developer?

A good front-end developer needs to have a working knowledge about:

·      HTML

·      CSS

·      JQuery

·      Javascript 

2) Explain how you would ensure that your web design is user-friendly and what kinds of steps would you use? 

A front-end developer needs to talk about working alongside UX(User Experience) designers to imagine and conceptualize a web page that cultivates a user-centric experience, testing the website with users to ensure optimal design and assuring the web page is optimized for mobile phone viewing.
 

3) Describe Coffee Script? 

CoffeeScript is a little programming language that compiles into JavaScript. It is an attempt to exhibit the good parts of JavaScript in a simple way. It also assists to write JavaScript code better by presenting you with a more constant syntax and skirting the unusual nature of JavaScript language.
 

4) Explain what is clear? 

A clear is utilized when you don’t need an element to wrap around another element, such as a float.
 

5) Explain What Is The Lazy Loading? 

Lazy loading is a design pattern commonly used in computer programming to defer initialization of an object until the point at which it is needed.

Lazy loading is loading code only once user needs it. For Example, there is a button on the page, which shows different layout once user pressed it. So there is no need to load code for that layout on initial page load.
 

6) Explain What Is The Difference Between Null And Undefined?

null is an object with no value. undefined is a type. 

typeof null; // "object" 

typeof undefined; // "undefined"
 

7) What Is Variable Scope? 

JavaScript variables have functional scope.
 

8) Explain What Is An Iife? 

IIFE stands for immediately-invoked function expression; it executes immediately after created by adding a () after the function.
 

9) What Is A Callback Function? 

JavaScript is read line by line. Sometimes, this can result in what seems like a subsequent line of code being executed prior to an earlier line of code. A callback function is used to prevent this from happening, because it is not called until the previous line of code has fully executed.
 

10) Tell Me Why Do We Recommend External CSS Or Javascript Versus Inline? 

Inline CSS or Javascript has bad impact on site performance.

Your HTML code will weigh more as you use inline scripts, whereas external scripts reduces HTML file size which helps fast rendering of webpage.

HTML code will never be cached so inline scripts. Contrary to that, external dependencies, such as CSS and JavaScript files, will be cached by the visitor's web browser. So it reduces https requests each time user click through web pages.

It is hard to maintain Inline CSS and Javascript code. Where having code in just one centralized location is a lot more preferable than changing exactly the same kind of code snippets spread all over the files in the web site.
 

11) Explain What "this" Is In Javascript? 

In JavaScript, 'this' normally refers to the object which 'owns' the method, but it depends on how a function is called.
 

12) Do You Know What Is Cors? How Does It Work? 

Cross-origin resource sharing (CORS) is a mechanism that allows many resources (e.g., fonts, JavaScript, etc.) on a web page to be requested from another domain outside the domain from which the resource originated. It's a mechanism supported in HTML5 that manages XMLHttpRequest access to a domain different.

CORS adds new HTTP headers that provide access to permitted origin domains. For HTTP methods other than GET (or POST with certain MIME types), the specification mandates that browsers first use an HTTP OPTIONS request header to solicit a list of supported (and available) methods from the server. The actual request can then be submitted. Servers can also notify clients whether "credentials" (including Cookies and HTTP Authentication data) should be sent with requests.
 

13) What is the difference between Json and Jsonp? 

JSONP is JSON with padding.
 

14) Explain how to use a Function A Class? 

function functionName(name) { 
this.name = name;
}

// Creating an object

var functionName = new functionName("WTEN"); 
console.log(functionName.name); //WTEN
 

15) Tell me how do you clear a Floated Element? 

clear:both
 

16) Can you tell us when would you utilize CSS float? 

Float is utilized when you need to make an element of your web page be pushed to the right or left and make other elements cover around it.
 

17) Can you explain the difference between visibility:hidden; and display:none? 

Visibility:Hidden; – It is not visible but gets up it’s original space.

Display:None; – It is hidden and takes no space.
 

18) Explain what is the difference between a host object and a native object? 

Host Objects  – are objects supplied by a particular environment.

Native Objects – are standard built-in objects given by Javascript.
 

19) What is the difference between XHTML and HTML? 

HTML and XHTML are both markup languages in which web pages are written. The main difference between the two is that HTML syntax is SGML based while XHTML syntax is XML based.
 

20) Explain what are the difference between Get and Post? 

A GET request is generally used for things like AJAX calls to an API, whereas a POST request is typically utilized to store data in a database or submit data through a form.

GET requests are limited secure and can be viewed by the user in the URL, whereas POST requests are used in two steps and are not seen by the user. So, POST requests are more secure.
 

21) Can you tell us when would you utilize CSS clear? 

When I want an element on the left or right of the floating element not to wrap around it, I can utilize clear.
 

22) Explain the importance of the HTML DOCTYPE? 

DOCTYPE is an instruction to the web browser regarding what version of the markup language the page is written. The DOCTYPE declaration need to be the pretty first thing in your HTML document, before thetag. Doctype declaration points to a Document Type Definition (DTD). It provides markup language rules, so a browser can interpret the content correctly. 

23) Explain the difference between cookies, session storage, and local storage? 

Cookies allow applications to store data in a client’s browser.
Session storage property allows applications to store data until the window is closed.
Local storage property lets applications to store data without an end.
 

24) Explain what is lazy loading? 

Lazy loading is a design pattern generally utilized in computer programming to delay initialization of an object until the period at which it is required. It can contribute to performance in the program’s operation if correctly and properly utilized. Besides, it is a loading code only once the user needs it. For instance, there is a button on the page, which reveals a different layout once the user pressed it. Hence, there is no necessary to load code for that layout on initial page load.
 

25) Explain the difference between classes and IDs? 

Classes and ID selectors, both are utilized as hooks for CSS styles. The ID’s are commonly used to style elements that only look once on a page, such as one instance of a navigational menu. The Classes are utilized to style different elements in the same fashion, such as the presence of links.
 

26) Explain what is Event Delegation? 

Event delegation points to the process of using event propagation to handle events at a higher level in the DOM than the element on which the event originated. It enables you to avoid adding event listeners to particular nodes; instead, you can add a single event listener to a parent element.
 

27) What is Ajax? 

AJAX (Asynchronous JavaScript and XML) allows applications to transport data to/from a server asynchronously without refreshing the page. This means that it is likely to update parts of a web page, without reloading the entire page. For instance, your new Gmail messages arrive and are marked as new even if you have not refreshed the web page.
 

28) What Is Stringify? 

stringify is used to transform JSON into a string.
 

29) Why do we need to use W3c Standard Code? 

The goals of such standards are to ensure cross-platform compatibility and more compact file sizes. The focus of these standards has been to separate "content" from "formatting" by implementing CSS. It eases maintenance and development.
 

30) How to clear a Floated Element? 

A floated element is taken out of the document flow. To clear it you would need to do a clear:both or try overflow:auto on the containing div.
 

31) What is a Float? 

Floats are used to push elements to the left or right, so other elements wrap around it.
 

32) How to optimize the Page using Front End Code or Technology? 

Below is the list of best practices for front-end technology, which helps to optimize page.

·      Improve server response by reducing resource usage per page

o   Combine all external CSS files into one file

o   Combine all external JS files into one file

·      Use responsive design instead of making device based redirects

·      Use asynchronous Javascript and remove block level Javascript

·      Use Minify version of stylesheet and javascript.

·      Optimize Image and use correct format of Image. Use the lazy loading design pattern for large size of images.

·      Use browser side cache with Cache control.

·      Avoid plugins to drive functionality.

·      Configure view port and use CSS best practices.

·      Prioritize visible content.

·      Load style-sheets in header and script in footer.
 

33) Have you ever used a CSS Preprocessor/Precompiler? What are the benefits? 

CSS preprocessors, such as SASS, have numerous benefits, such as variables and nesting.
 

34) Do you know what is the importance of the HTML Doctype? 

DOCTYPE is an instruction to the web browser about what version of the markup language the page is written. Its written before the HTML Tag. Doctype declaration refers to a Document Type Definition (DTD).
 

35) What is the difference between Responsive and Adaptive Development? 

In a nutshell, responsive is fluid and flexible, whereas adaptive adapts to the detected device/screen size.
 

36) Explain the difference between Inline, Block, Inline-block and Box-sizing? 

·      inline is the default. An example of an inline element is .

·      block displays as a block element, such as

·      inline-block displays an element as an inline-level block container. Here's an article on the topic.

·      box-sizing tells the browser sizing properties. 

37) Tell me where do you place your Javascript on the Page? 

It may depend on what you are using it for. There is some debate on this but generally a good question to ask to get an understanding of the JS knowledge.
 

38) Explain what is Web Application? 

A great question to feel out the depth of the applicants knowledge and experience.

A web application is an application utilizing web and [web] browser technologies to accomplish one or more tasks over a network, typically through a [web] browser.
 

39) What is the difference between Call and Apply? 

apply lets you invoke the function with arguments as an array. call requires the parameters to be listed explicitly. Also, check out this stackoverflow answer.
 

40) How to increase Page Performance? 

·      Sprites, compressed images, smaller images; 

·      include JavaScript at the bottom of the page; 

·      minify or concatenate your CSS and JavaScript; and 

·      caching.

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