jQuery Interview Questions_ and Answers
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Overview:- JavaScript is basically a scripting language of the web which the gadgets like Laptop, Smartphones, Personal Computers and even browser understand easily, and as a result, the bandwidth and the time of the server are saved. It means saving money. Developers use JavaScript to make the attractive web pages and user-friendly and attractive applications.

jQuery is actually a JavaScript library. jQuery has completely changed the way JavaScript is now written. It has become effortless to use JavaScript while building the website. While writing the JavaScript there are tasks which require some lines of JavaScript code and this can lead to a lengthy, ineffective and difficult to maintain the code. jQuery takes the entire common code and puts it in one file in a compressed form.

Development History:– The jQuery library was uniquely created by John Resig in  2006 at BarCamp New York City. John Resig was so impressed by the cssQuery (created by Dean Edward)that later he came up with the idea of creating a jQuery. jQuery is completely free and open-source software.

According to the data that got recorded in June 2018, 73% of the top websites in the world use jQuery and this is a remarkable achievement.

Latest Version:-The latest version of jQuery is 3.3.1 which got released on January 20, 2018. JQUERY3.0 and further supports the below mentioned browsers:-

  • Internet Explorer: 9+
  • Microsoft Edge, Mozilla Firefox, Google Chrome, Safari: Current and Current – 1
  • Opera: Current
  • Safari Mobile iOS: 7+
  • Android 4.0+

Advantages:-

  1. jQuery combines great practices of the programming
  2. jQuery application is effortless
  3. jQuery saves the server’s bandwidth
  4. jQuery runs on all the major browsers like Firefox, Google Chrome and Microsoft Edge
  5. The developer can add plugins as per the requirement in the programming.

Do you want to get success in the jQuery Interview Questions? Keep Reading!!!

Ques 1: Explain about jQuery.

jQuery is actually a javascript library. Jquery was created by John Resig in January 2006. jQuery was specifically designed to make the javascript coding effortless to use while building the attractive website and the applications. jQuery is the completely free open-source software. jQuery is the world’s most popular and the most used javascript library.

Ques 2: What do you mean by CDN?

CDN is an acronym for Control Delivery Network. Control Delivery Network is basically the unit of various servers which are located at various different locations. The task of these servers is to store the copy of the data with them so that the data request can be acknowledged by them based on the server which is nearest to the end user. Finally, the data reaches to the end user very quickly and the data less affected by the traffic.          

Ques 3:Can you explain about  JQuery.noConflict?

jQuery make use of  $ sign as an alias for jQuery. There are other libraries also which also make the use of “$” sign. Just to make sure that “$” is available for other libraries we use jQuery.noconflict();

Example.

<script src=”other_lib.js”></script>

<script src=”jquery.js”></script>

<script>

$.noConflict();

// Code that uses other libraries $ can follow here.

</script>

Ques 4: What is the main advantage of jQuery?

  • jQuery is effortless to implement.
  • jQuery is extensible.
  • jQuery supports cross-browser programming.
  • jQuery makes efficient use of resources.
  • jQuery is quickbecause it uses native CSS formats.

Ques 5: What is the role of $() in jQuery?

$() is used largely to return a jQuery object in the code. $() can also check whether an object exists or not.

Ques 6: What is the role of selectors in jQuery?

Selectors are fundamentally the formats which are used to recognise and operate the HTML elements. For example:-if we want to choose all the checkboxes in a web form then we can make use of [type=”checkbox”] selector.

<script>

var input = $( “form input:checkbox” )

.wrap( “<span></span>” )

.parent()

.css({

background: “green”,

border: “3px blue solid”

});

</script>

This is the best jQuery Interview Question particularly when you are an experienced candidate.

Ques 7: What do you mean by DOM in jQuery? How can we make sure that DOM is ready?

DOM is an acronym for  “Document Object Model”.  Document Object Model is a  treemap of all the HTML elements in web form which is loaded by the browser.

We can use .ready() method which gives a way to execute a JavaScript code as soon as the page’s Document Object Model becomes safe to manipulate.

Ques 8: Can you explain about the parent() in jQuery?

Parent() method in jQuery refers to the top-level elements in a given HTML object, which are normally selected by jQuery selector. Parent() method is used to manipulate the changes that have to be done at the top level of a nested HTML object. For Example,a paragraph which includes a couple of list elements can be a parent. Usually, Parent is used if there is an action which is based on the child element or if there is any special need for a parent to be treated differently.

Ques 9: Mention the difference between $(window).load and $(document).ready function?

$(window).load is provided by the browser in order to show that all the assets on the page (images, videos) are fully loaded. So if some calculation or user of assets is required in the code then it should happen after $(window).load is finished.

$(document).ready is used for the DOM object tree loading. This means that we can be certain that the DOM object is ready. It is important to note that DOM is loaded before page. So if you are trying to run any code which uses page assets it can fail.

Ques 10: What do you mean by toggle?

The toggle in jQuery is used to reverse the HTML element’s state. Toggle function can be used to check or uncheck a checkbox.


Ques 11: Can you tell the latest version of jQuery?

The latest version of jQuery is 3.3.1 which got released on January 20, 2018.

Ques 12: Mention the difference between the text() and HTML()?

S No. text() HTML()
1 The text() method in jQuery returnsthe text value inside an HTML element HTML() method in jQuery returns the entire HTML syntax
2 The text() method is used to only manipulate the value The HTML() method is used to manipulate the HTML object or the properties.

This is one of the most asked jQuery interview questions.

Ques 13: Mention the difference between jQuery and JavaScript?

S No. jQuery JavaScript
1 jQuery is a library for JavaScript only JavaScript is a scripting language which is used on browser or server-side
2 The developercannot write code in jQuery without the support of JavaScript. The developer can write code in JavaScript without jQuery

Ques 14: Can you explain the use of Each() function in jQuery?

Each() function is used to iterate arrays or collections of key-value pairs.

As a second argument, Each() functions accept a call back function which is executed for each value passed in the array. Each pair of the key value is accessed by call back function.

Ques 15:  List the difference between find and children methods in jQuery?

Find() is used to search for all elements across the DOM object. Children will look for only first level objects linked to a parent DOM object.

Ques 16: What do you mean by AJAX jQueryin and how it works?

AJAX stands for Asynchronous JavaScript and XML. AJAX is a unit of technologies that work collectively to give dynamic behaviour. This means users can enter the data on a web form, and without refreshing the whole page data can be sent to the server or data can be loaded from the server to browser. AJAX is used to load google map.

Ques 17: Mention the difference between size and length?

As length is a property and “size” is a method, length returns faster results. Both give a number of elements in an object.

Ques 18: Give a list of four parameters used for jQuery Ajax method

There are four important parameters in the AJAX call.

URL – address of the URL to be used to process the request

type – request type (is it a GET request or POST request)

data – data which is to be shared with the server

Cache – Instruction for a browser to cache the requested page or not.

Note: Go through this Question very thoroughly as this is one of the most important jQuery interview questions.

Ques 19: Name the program which is useful for testing jQuery?

The program that is used to test jQuery is called Qunit.

Ques 20: Can we use C# code in the code behind with jQuery?

As jQuery supports code-behind (ASP.NET) model we can use C# with jQuery.

Ques 21: How can you check whether an element is empty or not by usingjQuery?

We can make use of jQuery.isObjectEmpty() method to check whether an object is empty or not.

jQuery.isEmptyObject({}); // true

jQuery.isEmptyObject({ foo: “bar” }); // false

Ques 22: what is a class selector injQuery?

jQuery uses class selectors to identify HTML elements by the use of the CSS class. If all the elements having CSS class as “table row” needs to be search we can use a class selector for this.

Ques 23: Name the selector which is slowest injQuery?

jQuery has class selectors which are slowest in returning objects.

Ques 24: Name the selector which is fastest injQuery?

jQuery has ID and Element selectors which are fastest in returning objects.

Ques 25: Can we enhance user experience usingjQuery?

jQuery UI plugin which is a collection of animation effects, movable objects and other features to make the user interface highly interactive and easy to load for users.

Ques 26: Name the different methods used for giving visual effects injQuery?

jQuery has ID and Element selectors which are fastest in returning objects.

animate( parameters,

[duration, easing, callback]

) to make custom animations this function is used.

fadeIn( speed, [callback] ) to give the effect of “fading in” this function is used. It will fade in all matching elements.

fadeOut( speed, [callback] ) to give the effect of “fading out” this function is used. It will fade out all matching elements. It sets the opacity to 0 and then sets display property to “none”.

Ques 27: Can you explain ina jQuery process called chaining?

jQuery is a powerful feature of jQuery. It allows using multiple properties or functions to be used on a single element.

This reduces the code to be written. Also, the code is kept very easy to understand.

Chaining uses built-in functions making compilation bit faster.

Ques 28: How can you hide a block of HTML code on a button click by using jQuery?

The “.hide()”  method is used for hiding a specific element.

1 2 3 4 5 6 // With the element initially shown, we can hide it slowly: $( “#clickme” ).click(function() { $( “#notebook” ).hide( “slow”, function() { alert( “Animation Complete.” ); }); });

Ques 29: Explain jQuery Datepicker in jQuery?

jQuery UI has a highly configurable element called as Datepicker. This is used to customise the use of date functions for users. We can specify year range and whether to allow a year to be changed or not etc.

Ques 30: Can we remove a DOM Element in jQuery?

jQuery gives us different ways to eliminate a DOM object. We can use any of the following to do the task based on our specific use case:

  • empty()
  • remove()

Ques 31: Can we useEvents in jQuery?

jQuery uses events extensively. It is used to trigger a method or function call. Events are automatically attached once a jQuery is used on a web page. Events can be used with different methods on them like hover(),bind(),ready() etc.

Ques 32: Can we add CSS classes in jQuery?

jQuery gives us the flexibility to add a class to any element of HTML object. Following code demonstrates use a “addclass()” method.

$(‘#firstName’).addClass(“highlightClass”, “fast”)

Ques 33: Name the different operations we can do on CSS classes and DOM elements?

jQuery has the following methods to be used for removing a selected element class, for adding a class or switching a class:

1. .addClass (to add class)

2. .toggleClass (to toggle class)

3. .switchClass (to switch from one class to another)

4. .removeClass(to remove selected element class)

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