jQuery Interview Questions FAQ

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No. jQuery does not follow W3C standards. It uses non-standard properties and methods like innerHTML, as well as some browser-specific properties. It is nothing more than a library of pre-written methods and scripts that simplify basic javascript.

jQuery is a client side library written in JavaScript by John Resig. The client-side environment used to run scripts is usually a browser. The script is transferred from the web server to the users computer over the internet and run directly in the browser. It is important to note that the scripting language needs to be enabled on the client computer.

Server side programming has to do with generating dynamic content. We cannot classify languages as client side or server side. There could be a scenario where a server can execute Javascript and render HTML from it.

JQuery support cross browser and cross platform compatibility hence it simply runs on Windows, MAC, or Linux with all major browser compatibility.

jQuery code runs on the web browser.

In general, jQuery code is executed on the client side. But jQuery also give you the ability to call a particular function or action onto your server by sending 'xml-http Ajax request(jqXHR)' targeted specific server-side url, and receiving the response content in many different formats such as (html, Json, xml and so on).

The starting point of jQuery code execution is $(document).ready(function(){}) function that is executed when the DOM is loaded. The .ready() method offers a way to run JavaScript code as soon as the page's Document Object Model (DOM) becomes safe to manipulate.

There are several ways to start using jQuery on your web site. You can:

  1. Download a local copy from
  2. Link to a file via Content Delivery Network (CDN), like Google

Both Microsoft and Google already host jQuery on their CDNs. When to use jQuery from Google or Microsoft, use one of the following:

Google CDN

Microsoft CDN

If you wish to use jQuery CDN other than Google or Microsoft hosted jQuery library, you might consider using this and ensures uses the latest version of jQuery:

Yes. The "protocol-less" URL is the best way to reference third party content that's available via both HTTP and HTTPS. When a URL's protocol is omitted, the browser uses the underlying document’s protocol instead.

jQuery.noConflict() method allows you to use multiple JavaScript Libraries, while using jQuery. The noConflict() method releases the hold on the $ shortcut identifier, so that other scripts can use it.

It is always a great idea to wrap your Javascript code inside jQuery.ready(). You can use the explicit call

Or use the shortcut

By default, jQuery uses "$" as a shortcut for "jQuery".

You can use $ or jQuery signs. By default, jQuery uses "$" as a shortcut for "jQuery".

So, using $("#id") or jQuery("#id") is the same.

jQuery has many ways of accessing its library:

jQuery or window.jQuery can be used instead of $ if you were using more than one library.

Yes. You can use multiple document ready handler, there is no special advantage even though you can use jQuery code in several place. All will get executed on first called first run basis. It is important to note that each jQuery() call must actually return. If an exception is thrown in one, subsequent calls will never be executed.

The "#" is used to select by id:

It will select one and only one element which have id myID.

The '.' is used to select elements by class:

It will select all the elements which have class as myClass.

jQuery provides jQuery.browser property which returns the browser information. The $.browser property is deprecated in jQuery 1.3, and its functionality may be moved to a team-supported plugin in a future release of jQuery.

Jquery is a JavaScript library meant for dom operations. JQueryUI is adds to JQuery to provide interactive UI components such as buttons, tabs, sliders, drag and drop and more. Plus it provides a style theming system. It works with its own CSS files. jQuery is the core library. jQueryUI is built on top of it. If you use jQueryUI, you must also include jQuery.

  1. Hit the F12 key
  2. Select the Scripts, or Sources, tab in the developer tools
  3. Click the little folder icon in the top level
  4. Select your JavaScript file
  5. Add a breakpoint by clicking on the line number on the left
  6. Execute your JavaScript

QUnit is a powerful, easy-to-use JavaScript unit testing framework. It's used by the jQuery, jQuery UI and jQuery Mobile projects and is capable of testing any generic JavaScript code.

No, jQuery HTML only works for HTML documents not for XML Documents.

jQuery.min.js is a compressed version of jQuery.js. In terms of functionality, there is no difference between the jQuery.js and jQuery.min.js. The difference is only in whether it's formatted nicely for readability or compactly for smaller file size(jQuery.min.js).

You are able to read jQuery.js and understandable. The unnecessary characters are removed in jQuery.js.min for fast loading purposes and less size. The removal of whitespace removes line breaks and spaces messing up the formatting, and the shortening of variable names (including some function names) replaces the original variable names with meaningless letters. It is better using the minified version (.min) for your live environment as Search Engines are now checking on page loading times.

Yes you can, jQuery is a Javascript library, therefore the two can be used in the same file.

jQuery.noConflict() method allows you to use multiple frameworks, while using jQuery.

It is important to note that, even with noConflict it is possible for problems to occur. Libraries use different internal methods to manipulate events and DOM nodes. There is the possibility of subtle bugs that noConflict is unable to prevent.

Try a new alias to jQuery.

Selectors allow page elements to be selected. The frequently used type of selectors in jQuery are:

  1. ID Selector - Selects the element with the ID using the '#' keyword.

  2. Class Selector - Selects the element with the class name using the '.' keyword.

  3. Element Selector - Selects the element using its type Ex. $("p").

jQuery allows two ways to set width and height of any element. You can set using css or you can use jQuery provided methods. The difference between jQuery width() and css(width) is that the jQuery width() returns a unit-less pixel value (for ex. 100) while the css(width) returns a value with units intact (for ex. 100px). The jQuery width() method is recommended when an element's width needs to be used in a mathematical calculation.

jQuery.size() and jQuery.length both returns the number of element in an object. But the jQuery.length property is preferred because it does not have the overhead of a function call. Moreover, jQuery.size() deprecated in jQuery 1.8 and completely removed in jQuery 3.0.

The this is the DOM object and $(this) is jquery object wrapper around 'this' DOM object.

When using 'this' you can directly access the DOM node that's being processed, but not jQuery object. When using $(this), you can call jQuery methods on it, but not DOM object. In many cases it's better to use plain 'this'.

The jQuery $.find method may travel through multiple levels down to get the descendent elements. Whereas, the $.children method can go to just one level down.

$(element).parent() returns the immediate parent.
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