Front end Developer Interview Questions

Front end Developer Interview Questions
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Below are the list of Best Front end Developer Interview Questions and Answers

HTML (HyperText Markup Language) is a markup language to design the web page. It is used to display the contents of the web page in order. They are the building blocks of the HTML pages. This text-based markup language creates documents by denoting structural semantics.

The HTML elements such as headings, paragraphs, lists, links, quotes, and other items are delineated by tags. HTML was developed by WHATWG and first released in 1993.

Ajax (Asynchronous Javascript and XML) is a technique to create asynchronous web applications. Applications developed with Ajax can send and retrieve data asynchronously from the server without interfering with the existing page of the application. It sends and receives data in the background.

Ajax is not a single technology but a combination of technologies such as HTMML, CSS, DOM, JSON, XML, XMLHttpRequest, and JavaScript.

NPM stands for Node Package Manager. It is used to install, uninstall, update packages for Javascript Programming Language. NPM also is a default package manager for Node.js.

REST stands for Representational State Transfer. It is an architectural style that defines a set of standards to create web services or API.

LocalStorageSession storageCookie
localStorage is a way to store data on the client’s computer. It allows the saving of key/value pairs in a web browser and it stores data with no expiration date. localStorage can only be accessed via JavaScript and HTML5. However, the user has the ability to clear the browser data/cache to erase all localStorage data. It has key-value storage, where we have key and value as a serialized object. It has LocalStorage API from the console and it will create a key-value pair in the LocalStorage store.Session storage stores data only for a session, meaning that the data is stored until the browser (or tab) is closed. Session storage data is never transferred to the server. It can only be read on the client-side. Its storage limit is about 5-10MB. It provides opening multiple tabs/windows with the same URL creates sessionStorage for each tab/window.Cookie stores data that has to be sent back to the server with subsequent XHR requests. Its expiration varies based on the type and the expiration duration can be set from either server-side or client-side. Cookies are primarily for server-side reading (can also be read on client-side), localStorage and sessionStorage can only be read on the client-side. Size must be less than 4KB. Cookies can be made secure by setting the httpOnly flag true for that cookie. This prevents client-side access to that cookie. Cookies can be updated and set using document.cookie object from browser window object.

JSON-P (JSON with padding) is a technique of Javascript which allows you to return back to the JSON data from a remote server. When we create a script node dynamically with a cross-domain source then in case of returning Javascript function to a remote site there is a need for evaluation of that function. In the case of JSON, you can only get particular data from a remote server but in case you want to stick to the returned data then there is a need to use a Javascript function which is JSONP. It becomes easy to use JSONP with jQuery.

Event delegation model sometimes refers to the Delegation Event model. The Delegation Event model is a technique used to handle events in GUI (Graphical User Interface) based programming languages. The delegation event model provides standard and consistent mechanisms to generate and process events. its processes events are cleanly separated from the user interface logic that generates those events.

CSS sprites are a combination of multiple images into a single file that we use on our website. CSS sprites help us to load our page faster by reducing the number of file requests.

To clear float property is used to clear the float property after it is used on an element. You should match the cleat to the float when clearing it.

Mixins in CSS is used to define patterns of property-value pairs that can be reused. It is used by the document authors to group vendor prefixes and to simplify the code.

To define a mixin, the @mixin keyword should be followed by the mixin name with a declaration block.

//example of mixin definition
@mixin .rounded7px {
  -moz-border-radius: 7px;

The Grid layout in the CSS offers a grid-based system with rows and columns to place the HTML elements. It removes the need for using floats and positioning. It consists of one parent element and one or more child elements placed in rows and columns. This design system is supported in all modern browsers.

//example of the grid design system in CSS
<div class="grid-container">
  <div class="grid-item">1
  <div class="grid-item">2
  <div class="grid-item">3

There are three ways to include a CSS file in the web page. They are,

External CSS

Here, an external CSS file is linked to an HTML page to apply the changes created in that file.

//example of linking external CSS file
<link rel="stylesheet" type="text/css" href="mystyle.css">

Internal CSS

Here, a separate CSS block is inserted into the HTML page. This CSS code is defined within the </style> tag.

//example of </style> tag definition
body {
  background-color: black;

Inline CSS

Here, each CSS style is embedded in the HTML tags to apply style for than a single element.

//example of Inline CSS
<p style="color:red;">This is a paragraph.</p>