{"id":1015,"date":"2018-08-08T03:40:57","date_gmt":"2018-08-08T03:40:57","guid":{"rendered":"https:\/\/www.gologica.com\/blog\/?p=1015"},"modified":"2025-04-06T01:35:22","modified_gmt":"2025-04-06T01:35:22","slug":"javascript-interview-questions-and-answers","status":"publish","type":"post","link":"https:\/\/www.gologica.com\/elearning\/javascript-interview-questions-and-answers\/","title":{"rendered":"JavaScript Interview Questions and Answers"},"content":{"rendered":"

What are the advantages of using JavaScript?<\/strong>
\nLightweight: JavaScript can be executed within the user\u2019s browser without having to communicate with the server, saving on bandwidth.
\nVersatile: JavaScript supports multiple programming paradigms\u2014object-oriented, imperative, and functional programming and can be used on both front-end and server-side technologies.
\nSleek Interactivity: Because tasks can be completed within the browser without communicating with the server, JavaScript can create a smooth \u201cdesktop-like\u201d experience for the end user.
\nRich Interfaces: From drag-and-drop blocks to stylized sliders, there are numerous ways that JavaScript can be used to enhance a website\u2019s UI\/UX.
\nPrototypal Inheritance: Objects can inherit from other objects, which makes JavaScript so simple, powerful, and great for dynamic applications.<\/p>\n

Explain the difference between classical inheritance and prototypal inheritance?<\/strong>
\nThe great thing about JavaScript is the ability to do away with the rigid rules of classical inheritance and let objects inherit properties from other objects.
\nClassical Inheritance: A constructor function instantiates an instance via the \u201cnew\u201d keyword. This new instance inherits properties from a parent class.
\nPrototypal Inheritance: An instance is created by cloning an existing object that serves as a prototype. This instance\u2014often instantiated using a factory function or \u201cObject.create()\u201d\u2014can benefit from selective inheritance from many different objects.<\/p>\n

Give an example of a time that you used functional programming in JavaScript?<\/strong>
\nFunctional programming is one of the key paradigms that makes JavaScript stand out from other languages. Look for examples of functional purity, first-class functions, higher-order functions, or using functions as arguments and values. It\u2019s also a good sign if they have past experience working with functional languages like Lisp, Haskell, Erlang, or Clojure.<\/p>\n

Give an example of a time that you used Prototypal OO in JavaScript?<\/strong>
\nPrototypal OO is the other major programming paradigm that really lets JavaScript shine\u2014objects linked to other objects (OLOO). You\u2019re looking for knowledge of when and where to use prototypes, liberal use of \u201cObject.assign()\u201d or mixins, and a solid grasp of concepts like delegation and concatenative inheritance.<\/p>\n

What is a RESTful Web Service?<\/strong>
\nREST stands for Representational State Transfer, an architectural style that has largely been adopted as a best practice for building web and mobile applications. RESTful services are designed to be lightweight, easy to maintain, and scaleable. They are typically based on the HTTP protocol, make explicit use of HTTP methods (GET, POST, PUT, DELETE), are stateless, use intuitive URIs, and transfer XML\/JSON data between the server and the client.<\/p>\n\n\n\n
<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"Javascript<\/a><\/p>\n

Which frameworks are you most familiar with?<\/strong>
\nYou can tell a lot about a programmer from the frameworks they\u2019re familiar with\u2014AngularJS, React, jQuery, Backbone, Aurelia, and Meteor are just some of the more popular ones available. The key here is to make sure the developer you\u2019re engaging has experience with the framework you\u2019ve chosen for your project.<\/p>\n

How experienced are you with MEAN?<\/strong>
\nThe MEAN (MongoDB, Express, AngularJS, and Node.js) stack is the most popular open-source JavaScript software stack available for building dynamic web apps\u2014the primary advantage being that you can write both the server-side and client-side halves of the web project entirely in JavaScript. Even if you aren\u2019t intending to use MEAN for your project, you can still learn a lot about the developer when they recount their experiences using JavaScript for different aspects of web development.<\/p>\n

difference between document.ready and anonymous function in javascript<\/strong>
\nAnonymous function will be executed firs.
\nSelf-invoking functions runs instantly i.e will be executed as soon as it is encountered in the Javascript. $(document).ready(function() {})(); will trigger only after dom elements are completely constructed.
\nHow to you change the title of the page by javascript?
\ndocument.title = “new title”;<\/p>\n

Are you a team player? Give an example of a time when you had to resolve a conflict with another member on your team.<\/strong>
\nThere are many jobs associated with putting together an application, and chances are high that your new JavaScript developer will at the very least have to interface with a designer. You\u2019re looking for a developer who can communicate effectively when they need to, responds to emails, and knows how to coordinate with other branches of a project.<\/p>\n

Determine the output of the code below. Explain your answer.
\nvar lorem = { ipsum : 1};
\nvar output = (function(){
\ndelete lorem.ipsum;
\nreturn lorem.ipsum;
\n})();<\/p>\n

console.log(output);
\nThe output would be undefined, because the delete operator removed the property \u201cipsum\u201d from the object \u201clorem\u201d before the object was returned. When you reference a deleted property, the result is undefined.<\/p>\n

Explain the differences between one-way data flow and two-way data binding?<\/strong>
\nThis question may seem self-explanatory, but what you\u2019re looking for is a developer who can demonstrate solid understanding of how data flows throughout the application. In two-way data binding, changes to the UI and changes to the model occur asynchronously\u2014a change on one end is reflected on the other. In one-way data binding, data only flows one way, and any changes that the user makes to the view will not be reflected in the model until the two are synced. Angular makes implementing two-way binding a snap, whereas React would be your framework of choice for deterministic one-way data flow.<\/p>\n

What is the output of 10+20+”30″ in JavaScript?<\/strong>
\n3030 because 10+20 will be 30. If there is numeric value before and after +, it is treated is binary + (arithmetic operator).<\/p>\n\n\n\n
<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"JavaScript<\/a><\/p>\n

Difference between Client side JavaScript and Server side JavaScript?<\/strong>
\nClient side JavaScript comprises the basic language and predefined objects which are relevant to running java script in a browser. The client side JavaScript is embedded directly by in the HTML pages. This script is interpreted by the browser at run time. Server side JavaScript also resembles like client side java script. It has relevant java script which is to run in a server. The server side JavaScript are deployed only after compilation.<\/p>\n

In which location cookies are stored on the hard disk?<\/strong>
\nThe storage of cookies on the hard disk depends on OS and the browser.
\nThe Netscape navigator on Windows uses cookies.txt file that contains all the cookies. The path is : c:\\Program Files\\Netscape\\Users\\username\\cookies.txt
\nThe Internet Explorer stores the cookies on a file username@website.txt. The path is: c:\\Windows\\Cookies\\username@Website.txt.<\/p>\n","protected":false},"excerpt":{"rendered":"

What are the advantages of using JavaScript? 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