Top 25 jQuery interview question in 2020

  1. Question: What is jQuery UI?

Answer: JQuery UI, is a framework built on top of JQuery with effects, widgets, and central themes which mainly depend upon the JavaScript library. If you need to build a web application with high interaction or want to add a date picker to a form control(For example, like we did here), then JQuery UI is a great option.

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  1. Question: What is jQuery Mobile?

Answer: jQuery Mobile is a UI framework built on top of the Core of JQuery. The primary goal of JQuery Mobile is to develop websites that are responsive and mobile-accessible applications which also support tablets and other devices. JQuery Mobile uses HTML5 & CSS3 for laying out pages. If you’d like to build a JQuery mobile app, check out this post.

  1. Question: What is jQuery?

Answer: jQuery is a Javascript library that makes DOM manipulation, event handling, animation, and Ajax requests simpler and more efficient. jQuery has a simple to use API that works great across all modern browsers. JQuery greatly reduces the lines of code needed to achieve the same results in vanilla Javascript. Basically, jQuery simplifies the use of the JavaScript language.

  1. Question: What are Events?

Answer: Event-handling is responding to user actions on a webpage- in JQuery these actions are called events. JQuery provides simple methods for attaching event handlers to DOM elements or selections. This way, the provided function is executed when an event occurs.

  1. Question: What types of jquery Events are there?

Answer: The common DOM events are:

  • Form

  • Keyboard

  • Mouse

  • Browser

  • Document Loadingjquery quiz interview questions

  1. Question: What is $() in jQuery? 

Answer: $ is a reference to the jQuery namespace. With it, you can access its static methods, while $() calls a function that either registers a DOM-ready callback  if a function is passed to it, or returns elements from the DOM, if a selector. $() as a selector is used to select elements. 

  1. Question: What are ID selectors in jQuery?

Answer: ID selectors are the same as they are in CSS. ID selectors use ID to select just one element. 

  1. Question: What are class selectors in jQuery?

Answer: Class selectors use a class to select elements. If you want to select a group of elements with the same CSS class, you can use the class selector.

  1. Question: What is the difference between onload() and document.ready() methods?

Answer: Class selectors use a class to select elements. If you want to select a group of elements with the same CSS class, you can use the class selector.

  1. Question: What is the use of css() method in JQuery?

Answer: The jQuery CSS() method is used to get (return)or set the value of a computed style property for the first element in the set of matched elements or set one or more CSS properties for every matched element. The first argument is the css property name, and the second argument is the value to set for the property.

  1. Question: What is jQuery Ajax?

Answer: AJAX stands for Asynchronous JavaScript and XML and its used to help us load data and exchange data with a server without a browser refresh. JQuery has an array of AJAX methods to help accomplish this. The ajax() method sends an asynchronous http request to the server.

  1. Question: What are some benefits of jQuery Ajax methods?

Answer: A few advantages include: 

  • Ability to send GET and POST requests

  • Ability to Load JSON, XML, HTML or Scripts

  • Cross-browser support

  1. Question: Compare onload() and document.ready().

Answer: The Onload() event will be called only after the DOM and resources like images get loaded, but jQuery's document.ready() event will be called when the DOM is loaded (doesn’t wait for ressources). 

  1. Question: What is jquery.min.js?

Answer: jquery.min.js is a compressed version of jquery.js used in order to preserve bandwidth.It has the same functionality as jquery.js, but whitespaces and comments are removed, shorter variable names are used, etc. It is always better to use this compressed version in the production environment as the web page loads more efficiently. 

  1. Question: What the Zoom plug-in for jQuery?

Answer: Zoom is a plug-in for the jQuery Javascript library. It is a highly flexible tool that allows you to magnify iamges. 

  1. Question: What are plug-ins in jQuery?

Answer: JQuery plugins are used to extend jQuery's functionality. This is done by extending the prototype object. This wat, you enable all objects to inherit any methods that you add. Whenever you call jQuery() you're creating a new jQuery object, and all the methods get inherited.

  1. Question: What is chaining in jQuery?

Answer: This is also referred to as Query Method Chaining and allows us to run multiple jQuery commands in sequence on the same element(s). Using chaining, browsers don’t need to find the same element(s) more than once. To use this method, you simply append the next action to the previous action.

  1. Question: What is the filter method in jQuery?

Answer: The filter() method filters out elements that do not match the selected criteria. Filter() then returns those matches. 

  1. Question: What is the find method in jQuery?

Answer: Find() is used to find all the child elements of the selected element. 

  1. Question: What are all the ways to include jQuery on a page?

Answer:

  1. Include the .js file or .min.js file into the html document.

  2. Include JQuery inside the <script> tags in <head> or <body> tag: 

    1. <script src='jquery-3.2.1.min.js'></script>

  1. Write the code within the HTML document inside the <script> tag. 

21. Question: What is jQuery.noConflict?

Answer: If we have to use a JS library along with jQuery, the control of $ is given to the JS library (In jQuery, $ is just an alias for jQuery, so we don’t need to use $). To give this control, we use jQuery.noConflict(). It can also be used to assign a new name to a variable.

22. Question: What are the benefits of jQuery?

Answer: The advantages are:

  • Simple syntax and easy to use

  • Reduces lines of code as opposed to vanilla Javascript 

  • Has extensive documentation

  • Deals with cross-browser compatibility issues 

  • Lightweight and Open-source library.

  • Extensible and fast

  • Easy DOM manipulation 

  • Event handling & AJAX support.

23. Question: What is Qunit?

Answer: A unit testing framework for JQuery. It's used by jQuery, jQuery UI, and jQuery Mobile and is powerful, easy-to-use, and capable of testing any JavaScript code.

24. Question: Why host jQuery using a CDN?

Answer: A CDN (Content Delivery Network or Content Distribution Network) is a large distributed system of servers that reside in multiple data centers. CDNs are used to provide files from servers faster and therefore loading JQuery from a CDN would make it load faster. 

25. Question: Can jQuery be used for server scripting?

Answer: jQuery was only designed for client-side scripting and is not compatible with server-side scripting.

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