Jquery is an optimized lightweight JavaScript Library. It helps to develop more functional applications using less line of codes. You can say Jquery is the enhanced version of JavaScript. It contains many in-built functions to interact with HTML & JavaScript. You can download Jquery from jquery.com. Jquery is popular due to its reuse-ability. Jquery saves programmer time. For your successful interview read our Jquery Interview Questions and Answers. These Jquery interview questions are useful for both Experienced & Freshers professionals.
Why use JQuery over plain JavaScript?
Cross-Browser Compatibility: jQuery handles browser inconsistencies, ensuring code works uniformly across different browsers.
Simplified Syntax: jQuery reduces verbose JavaScript code with shorter, more readable methods.
DOM Manipulation: Selecting and modifying DOM elements is easier with jQuery’s selector engine.
AJAX: jQuery simplifies asynchronous HTTP requests with methods like `$.ajax()`.
Extensibility: Plugins and custom functions can be easily integrated.
25 Selective, Frequently asked Jquery Interview Questions and Answers
A compilation of interview questions related to jQuery is available for those preparing for technical assessments. It is essential to focus on the specific language required for responses and adhere to any relevant guidelines during the interview process. This resource aims to assist candidates in understanding key concepts and functionalities of jQuery, ensuring they are well-prepared to demonstrate their knowledge effectively.
1. What is the difference between Jquery & JavaScript?
JavaScript is a programming language formalized in the ECMAScript standard. When Jquery is a library developed using JavaScript. Jquery contain many common used JavaScript functions. Using Jquery we can prepare cross-browser compatible applications with less line of codes. Compare to JavaScript Jquery save time of a programmer & Applications developed using Jquery is easy to debug.
2. What you required to Start you first Hello World program using Jquery?
To start with Jquery “Hello World” program you need a text editor and the downloaded version of Jquery file. You can download Jquery file from jquery.com. To integrate this on your page you can refer the line below.
<script type="text/javascript" src="jquery.min.js"></script>
After integrated Jquery file in your HTML page. Write the following lines of code.
$document.ready(function() {
alert('Hello World!');
});
3. What is document.ready() method in Jquery?
Document.ready() method is used to execute Jquery after the HTML Document loaded to the Client Browser. In below I am sharing my first Jquery program to show you an example of document.ready() method.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
alert('My First Jquery Program.');
});
</script>
</head>
<body>
My First Jquery Program.
</body>
</html>
4. How to select all elements in a page using Jquery?
Using all selector in Jquery we can select all elements in a HTML page. Syntax used to select all elements is *. Look at the example below. In document.ready method here I am applying font style to all elements in a HTML page.
$("*").css("font-size", "14px");
5. What are the different type of Selectors available in Jquery?
jQuery selectors are used to find and select HTML elements based on their name, ID, classes, types, attributes, values, and more. Once selected, these elements can be manipulated using jQuery methods. In Jquery we have 3 types of Selectors. These are CSS selector, Xpath selector & Custom selector.
6. Explain me the show & hide methods in Jquery?
Show & hide are the ready-made methods of Jquery to Show or Hide any HTML element. Using show or hide methods in Jquery we can also add duration for showing or hiding an element. Show and Hide methods in Jquery accepts 2 parameters speed & callback. Look at the example below using Jquery Show & Hide methods.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('#btnShow').click(function() {
$('#txtLabel').show();
});
$('#btnHide').click(function() {
$('#txtLabel').hide();
});
});
</script>
</head>
<body>
<div id="txtLabel">This is a sample text.</div>
<button id="btnShow">Show</button>
<button id="btnHide">Hide</button>
</body>
</html>
7. What are the advantages using Jquery?
Jquery is a JavaScript Library which gives ability to develop high performance web applications using less line of Codes. There are many advantages using Jquery.
A. Jquery is Cross-browser Compatible. With Jquery stuffs we don’t need to worry about Browser Compatibility.
B. Jquery is easy to learn & implement. To do a small animation in client-side we must need to write 10 to 15 lines of JavaScript codes. Using Jquery this can be done using one function. Jquery comes with many in-built functions. Jquery improves programers time by delivering quality outputs.
C. Jquery helps to improve the performance of a web-application.
D. In a HTML Document Jquery is easy to use for DOM manipulation & traversal.
E. Jquery Supports Event detection and handling.
F. Jquery is rich with AJAX Capability. Thousand of free plugins are available for Jquery.
8. What is jQuery noConflict method?
JQuery uses $ sign as the alias. There are many other JavaScript libraries those uses $ sign. To prevent conflict with other libraries methods or different versions of JQuery, JQuery introduced noConflict method. You can use noConflict using the following Syntax.
$.noConflict();
Let’s assume in your application you want to use two versions of JQuery. Version 1.1.2 & Version 1.1.3. In this case to prevent conflict among the different versions you can do the following.
<script type="text/javascript" src="http://example.com/jquery-1.1.2.js"></script> <script type="text/javascript"> var jquery-112 = $.noConflict(true); </script> <script type="text/javascript" src="http://example.com/jquery-1.1.3.js"></script> <script type="text/javascript"> var jquery-113 = $.noConflict(true); </script>
9. How do you disable or enable a form element using Jquery?
Let we have an input box with id txtName. Two more buttons are there btnEnable & btnDisable. On click of enable button I want to enable the input box & on click of disable button I want to disable the input control. Look at the example below.
$('#btnEnable').click(function() {
$('#txtName').attr('disabled', false);
});
$('#btnDisable').click(function() {
$('#txtName').attr('disabled', true);
});
10. How to Change href attribute of an anchor tag using JQuery?
JQuery provides attr() method to change control attributes. Let us assume we have a button control with id “btn1”. On this button click we want to assign link to a anchor tag named “link1”.
$('#btn1').click(function() {
$('#link1').attr('href','http://google.com');
});
11. How to Valid an email using JQuery?
To valid email id using JQuery create a separate function ValidEmail(). Pass the email id as a parameter. Using Regex we can valid the email id. Example shown below.
function ValidEmail(EmailID) {
var filter = /^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/;
if (filter.test(EmailID)) {
return true;
}
else {
return false;
}
}
12. What is JQuery Selector? Explain me with Example.
JQuery selectors used to select group of HTML elements. Additionally JQuery supports CSS & ID Selector. JQuery Selector always starts with a dollar sign & parentheses. In case of we want to select all the div’s using Jquery Selector. The Syntax is as follows.
$(div)
Using CSS selector in JQuery we can select a control from its CSS class name. Let us we have a div with class “StyleDiv”. CSS Selector in JQuery uses dot with the class name to select the element. It can be selected using the following CSS selector.
$('.StyleDiv')
About ID Selector in JQuery we can select a control which have an ID. Let us we have a div with ID “MasterDiv”. ID selector is the most fastest JQuery selector compare to other selectors. It can be used using the following Syntax. # is the key to select a control using ID.
$('#MasterDiv')
13. Explain the animate function in JQuery.
The animate() function in jQuery is a robust tool for creating dynamic, engaging web animations with minimal effort. By understanding its parameters, leveraging callbacks, and following best practices, developers can enhance user experience while maintaining clean, efficient code. Whether animating simple movements or complex sequences, jQuery’s `animate()` function remains an indispensable asset in modern web development. In a HTML page for Client side animations JQuery provides animate function. Animate function accepts 4 parameters. Syntax of Animate function is as below.
$(selector).animate({params}, [duration], [easing], [callback])
Param defines CSS property on which we want animation. Using Duration we can set how long our animation will run. Easing is the controller to transition. Callback is the function which you can run just after the animation completed.
14. What is jQuery.holdReady() function?
Using jQuery.holdReady() function we can hold or release the execution of jQuery ready event in a HTML page. Jquery holdReady function accepts boolean parameters. To hold the execution we can write the following syntax.
When we want to release the ready event we need to set holdReady to false as shown below.