Top 51 jQuery Interview Questions And Answers

Question 1

What is jQuery?

Accepted Answer

**jQuery** is **fast, lightweight and feature-rich** client side JavaScript Library/Framework which helps in to traverse HTML DOM, make animations, add Ajax interaction, manipulate the page content, change the style and provide cool UI effect. It is one of the most popular client side library and as per a survey it runs on every second website.

Question 2

Is jQuery a library for client scripting or server scripting?

Accepted Answer

Client side scripting.

Question 3

Can we have multiple `document.ready()` function on the same page?

Accepted Answer

**YES**. We can have any number of document.ready() function on the same page.

Question 4

How do you select element by `ID` in jQuery?

Accepted Answer

To select element use ID selector. We need to prefix the id with "#" (hash symbol). For example, to select element with ID "txtName", then syntax would be,

```js
$('#txtName')
```

Question 5

What is a _CDN_?

Accepted Answer

A content delivery network or content distribution network (CDN) is a large distributed system of servers deployed in multiple data centers across the Internet. The goal of a CDN is to serve content to end-users with high availability and high performance.

There are 3 popular jQuery CDNs:

1.  1\. Google.
2.  2\. Microsoft
3.  3\. jQuery.

Advantages of using CDN:

*   It reduces the load from your server.
*   It saves bandwidth. jQuery framework will load faster from these CDN.
*   The most important benefit is it will be cached, if the user has visited any site which is using jQuery framework from any of these CDN

Question 6

Is jQuery replacement of JavaScript?

Accepted Answer

**No.** jQuery is not a replacement of JavaScript. jQuery is a different library which is written on top of JavaScript. jQuery is a lightweight JavaScript library that emphasizes interaction between JavaScript and HTML.

Question 7

Why do we use jQuery?

Accepted Answer

Due to following advantages.

*   Easy to use and learn.
*   Easily expandable.
*   Cross-browser support (IE 6.0+, FF 1.5+, Safari 2.0+, Opera 9.0+)
*   Easy to use for DOM manipulation and traversal.
*   Large pool of built in methods.
*   AJAX Capabilities.
*   Methods for changing or applying CSS, creating animations.
*   Event detection and handling.
*   Tons of plug-ins for all kind of needs.

Question 8

Is jQuery a W3C standard?

Accepted Answer

No. jQuery is not a W3C standard.

Question 9

What is `jQuery.noConflict`?

Accepted Answer

As other client side libraries like MooTools, Prototype can be used with jQuery and they also use `$()` as their global function and to define variables. This situation creates conflict as `$()` is used by jQuery and other library as their global function. To overcome from such situations, jQuery has introduced `jQuery.noConflict()`.

```js
jQuery.noConflict();
// Use jQuery via jQuery(...)
jQuery(document).ready(function(){
   jQuery("div").hide();
});  
```

You can also use your own specific character in the place of `$` sign in jQuery.

```js
var $j = jQuery.noConflict();
// Use jQuery via jQuery(...)
$j(document).ready(function(){
   $j("div").hide();
});  
```

Question 10

What is the use of jQuery `.each()` function?

Accepted Answer

The `$.each()` function is used to iterate over a jQuery object. The `$.each()` function can be used to iterate over any collection, whether it is an object or an array.

Top 51 jQuery Interview Questions

What is jQuery?

Why do we use jQuery?

What is the difference between .js and .min.js files?

How JavaScript and jQuery are different?

Is jQuery a library for client scripting or server scripting?

Is jQuery a W3C standard?

What is jQuery.noConflict?

How do you select element by ID in jQuery?

What does dollar sign ($) means in jQuery?

What is the use of jQuery .each() function?

Which is the starting point of code execution in jQuery?

What is event.PreventDefault()?

Is jQuery replacement of JavaScript?

What is a CDN?

Can we have multiple document.ready() function on the same page?

What is the difference between parent() and parents() methods in jQuery?

Which is fast document.getElementByID('txtName') or $('#txtName')?

What is the difference between jquery.size() and jquery.length?

What is difference between prop and attr?

What is the difference between eq() and get() methods in jQuery?

What are various methods to make ajax request in jQuery?

When would you use AngularJS vs jQuery?

What are selectors in jQuery and how many types of selectors are there?

What are the fastest/slowest selectors in jQuery?

Difference between $(this) and this in jQuery?

What is chaining in jQuery?

Is there any difference between body.onload() and document.ready() function?

How to create clone of any object using jQuery?

What is the difference between event.PreventDefault() and event.stopPropagation()?

Is there any advantage of using $.ajax() for ajax call against $.get() or $.post()?

How do you attach a event to element which should be executed only once?

In what situation you would use multiple version of jQuery and how would you include them?

Explain .bind() vs .live() vs .delegate() vs .on()

What is the difference between $('div') and $('<div/>') in jQuery?

What are the differences between JavaScript's window.onload and jQuery's $(document).ready() method?

How can I get jQuery to perform a synchronous, rather than asynchronous, Ajax request?

What is the difference between event.PreventDefault() and return false?

How does caching helps and how to use caching in jQuery?

Is there any significant difference between event.preventDefault() vs. return false to stop event propagation?

What are deferred and promise object in jQuery?

What is the difference between event.stopPropagation and event.stopImmediatePropagation?

How can I implement my own $(document).ready functionality without using jQuery?

Is it possible to hold or delay document.ready execution for sometime?

Is it possible to get value of multiple CSS properties in single statement?

What is the advantage of using protocol less URL while referencing jQuery from CDNs?

How to select element having a particular class (.selected)?

What does $('div.parent') will select?

What does $("div") will select?

How jQuery selectors are executed?

What is wrong with this code line $('#myid\\.3').text('blah blah!!!');

Can we execute/run multiple Ajax request simultaneously in jQuery? If yes, then how?

What is the difference between `.js` and `.min.js` files?

What is `jQuery.noConflict`?

How do you select element by `ID` in jQuery?

What does dollar sign (`$`) means in jQuery?

What is the use of jQuery `.each()` function?

What is `event.PreventDefault()`?

Can we have multiple `document.ready()` function on the same page?

What is the difference between `parent()` and `parents()` methods in jQuery?

Which is fast `document.getElementByID('txtName')` or `$('#txtName')`?

What is the difference between `jquery.size()` and `jquery.length`?

What is difference between `prop` and `attr`?

What is the difference between `eq()` and `get()` methods in jQuery?

Difference between `$(this)` and `this` in jQuery?

Is there any difference between `body.onload()` and `document.ready()` function?

What is the difference between `event.PreventDefault()` and `event.stopPropagation()`?

Is there any advantage of using `$.ajax()` for ajax call against `$.get()` or `$.post()`?

Explain `.bind()` vs `.live()` vs `.delegate()` vs `.on()`

What is the difference between `$('div')` and `$('<div/>')` in jQuery?

What are the differences between JavaScript's `window.onload` and jQuery's `$(document).ready()` method?

What is the difference between `event.PreventDefault()` and `return false`?

Is there any significant difference between `event.preventDefault()` vs. `return false` to stop event propagation?

What are `deferred` and `promise` object in jQuery?

What is the difference between `event.stopPropagation` and `event.stopImmediatePropagation`?

How can I implement my own `$(document).ready` functionality without using jQuery?

Is it possible to hold or delay `document.ready` execution for sometime?

How to select element having a particular class (`.selected`)?

What does `$('div.parent')` will select?

What does `$("div")` will select?

What is wrong with this code line `$('#myid\\.3').text('blah blah!!!');`