Jquery Interview Questions: Part 1

Jquery Interview Questions: Part 1
Jquery Interview Questions: Part 1

Introduction

As we all know, Javascript is one of the most powerful and frequently used web programming languages. However, javascript can be challenging to develop at times. Thankfully, jQuery comes into play and allows us to write less and accomplish more. jQuery is a lifesaver for many developers and is frequently used in the development industry.

I’m sure you’re aware of all of this, but let’s go through the use of Jquery one more time to grasp the jquery interview Questions better. jQuery is a robust and frequently used JavaScript framework for simplifying basic web programming tasks.

jQuery is frequently used on websites to provide unique features. The use of websites and web apps with various capabilities is rising these days. As a result, there is a high demand for front-end developers proficient in jQuery with HTML and CSS.

To start their careers as Front End Developers, candidates must crack an interview in which they are asked various jQuery interview questions.

Now, you are ready to learn the questions we have prepared for you. This blog will cover the Basic and Intermediate level jQuery Interview Questions, followed by the Advanced Level Questions in Part 2.

Source: Reddit

Jquery Interview Questions 

  1. What is jQuery?

jQuery is an open-source, lightweight, and widely used JavaScript library created to simplify interactions between an HTML or CSS document and JavaScript. jQuery is based on the principle “write less, accomplish more.”

  1. What can you do using jQuery?
  • You can quickly build effects such as show or hide elements, sliding transitions, and so forth.
  • With fewer lines of code, you can quickly build sophisticated CSS animation.
  • DOM elements and their properties are simple to modify.
  • Ajax can be simply implemented to allow for asynchronous data flow between client and server.
  • You can simply manipulate components by selecting them.
  • You can quickly navigate the DOM tree to find any element.
  • With a single line of code, you can quickly perform numerous actions on an element.
  • HTML element dimensions may be readily obtained or changed.

The list does not stop here; there are several other intriguing things you can accomplish using jQuery. 

  1. What are the advantages of jQuery over javascript?

For efficient web development, jQuery simplifies HTML document traversal, event handling, animation, and Ajax interactions. Compared to JavaScript and its other JavaScript libraries, jQuery is simpler to use and requires minimal lines of code to be written.

For example:

Let us see the following code snippet as an example of jQuery and JavaScript to change the background color:

blog banner 1

JavaScript

function changeColor(color) {
// changing the background color of the document with the passed color

   document.body.style.background = color; 
}
// function call
OnLoad=”changeColor('blue');”

jQuery

$ ('body') .css ({'background', '#0000FF'});

As demonstrated above, both code pieces perform the same thing; they change the background colour. However, jQuery requires less code and is easier to use.

  1. What are the differences between jQuery and javascript?

Some of the differences are as given below:-

jQueryJavascript
jQuery is not a programming language rather a javascript Library or framework.Javascript is a dynamic and interpreted programming language for web development.
It is a straightforward approach.It is a lengthy and hard-to-code approach.
The only thing the user needs to do is write the necessary jQuery code, making it less time-consuming.The user must write the entire js code. Thus, it is more time-consuming as the whole script needs to be written.
There is no need to deal with multi-browser compatibility troubles.Developers write their code to handle multi-browser compatibility.
The URL of the jQuery library must be included in the page’s header.All browsers support JavaScript. Any other plugins are not required.
It is dependent on JavaScript because it is a js library.jQuery is a module of javascript. As a result, the js code may or may not be dependent on jQuery.
jQuery is an optimized technique for web designing.JavaScript is one of the most popular web design programming languages for developers, and it is responsible for the emergence of jQuery.
jQuery speeds up the creation of DOM.JavaScript is sluggish when it comes to generating DOM.
  1. Explain the Advantages of jQuery in brief?

jQuery has the following advantages:

  • Clean and easy to use.
  • The syntax is simple and clear.
  • Open coding standards that are straightforward to use.
  • Deals with cross-browser conflicts without requiring the developer to worry about them.
  • The core library is small, at 24kb in size.
  • It is an open-source library.
  • A comprehensive collection of animations and effects.
  • Extensible and quick.
  • It can be optimised for search engines to improve SEO.
  1. What is $() in jQuery library?

The $() function is an abbreviation for the jQuery() function. It is used to wrap any object into a jQuery object, allowing you to call the many methods offered by the jQuery object. If you give a selector string to the $() method, it will return a jQuery object with an array of all matched DOM elements.

Syntax:

$(selector)
  1. What is a CDN?

In layman’s terms, a Content Delivery Network (CDN) is a network of servers located worldwide. In other words, a CDN is a network of servers that routes each request to the nearest server.

The Need for a CDN: 

Data for every online application can be classified as static or dynamic content. Dynamic material is often derived from a database. CSS, images, JavaScript, flash files, video files, and other forms of static content are examples.

Source:- Hacker Noon

Advantage of Using the CDN

When visiting another website, many people have already downloaded jQuery from Google. Consequently, when people visit your site, it will be loaded from the cache, resulting in a quicker loading time. Furthermore, most CDNs will ensure that when a user requests a file from it, it will be provided from the server nearest to them, resulting in a quicker loading time.

  1. Mention the compatible operating systems with jQuery.
  • Mac
  • Windows
  • Linux
  1. Can you use multiple document.ready( ) on the same page?

Yes. On the same page, you may use as many document.ready() functions as you like.

For example:

$(document).ready(function() {    
$("h1").css("background-color", "yellow" );    
 });    
$(document).ready(function() {    
$("#para").css("border", "3px dotted blue" );    
 });   

In the above example, we attempt to make the h1 tag’s background colour yellow. Following that, in the ready( ) method, whichever element has the para id will have its border changed to 3px dotted blue.

  1. Can you use any other name in place of $( ) in jQuery?

Yes, we can use jQuery as a function name instead of $ (dollar symbol). 

Many JavaScript libraries, including jQuery, utilise $ as a function or variable name. In jQuery, $ is only an alias for jQuery; therefore, all functionality is available without using $.

As an example:

jQuery(document).ready(function() {    
jQuery("body").css("background-color", "yellow");    
});
  1. What are the effects methods used in jQuery?

We can use jQuery to add effects to a web page. jQuery effects are classified as fading, sliding, hiding/showing, and animation. jQuery has a plethora of techniques for creating effects on a web page.

Some of the ways that generate the effect are given below:

clearQueue()Removes any remaining pending functions from the components that have been chosen.
delay()Sets a delay for all queued functions on the selected elements
dequeue()Removes the next function from the queue before running the function.
fadeIn()Fades in the chosen elements
fadeOut()Fades out the selected elements
fadeTo()The selected components are faded in and out to a specified opacity.
fadeToggle()The fadeIn() and fadeOut() functions are toggled.
finish()All queued animations for the chosen items are stopped, removed, and completed.
hide()Hides the selected elements
queue()Shows the functions that have been queued on the selected elements.
show()Shows the selected elements
slideDown()Slides-down (shows) the selected elements
slideToggle()Toggles between the slideUp() and slideDown() methods
slideUp()Slides-up (hides) the selected elements
stop()Stops the current animation for the elements that have been selected.
toggle()Toggles between the hide() and show() methods
animate()Runs a custom animation on the elements you’ve selected.
  1. Is jQuery a javascript or JSON file?

jQuery is described as a single JavaScript file library that comprises DOM/CSS manipulations, event effects or animations, AJAX methods, and several extensively used plugins. In contrast, JSON is a text format that is completely language independent.

  1. What is the use of the toggle( ) method in jQuery?

The jQuery toggle() function is a particular sort of method that is used to switch between the hide() and show() methods. It shows the hidden elements and hides the shown element.

In simple words, This method examines the visibility of the elements that have been selected. If an element is hidden, show() is called. If an element is visible, hide() is called, resulting in a toggling effect.

Syntax:

$(selector).toggle(speed,easing,callback)
  • Speed:- Optional. The pace of the hide/show effect is specified here.
  • Easing:- Optional. Specifies the element’s speed at various stages throughout the animation. “swing” is the default value.

Possible values:-

 “Swing” – moves slower at the beginning/end but faster in the middle.

 “linear” – move at a constant speed.

  • Callback:- Optional. A function to be executed after the toggle( ) method is completed.
  1.  Does jQuery work for both HTML and XML documents?

No, JQuery does not support XML documents. It is only applicable to HTML documents.

  1.  What is the starting point of the code execution in jQuery?

The $(document).ready() method is when jQuery programming begins. It is executed when the DOM is loaded. The ready() method will be loaded as soon as the DOM is loaded and before the page contents. This method should be wrapped around your javascript code to guarantee execution only when the page is fully displayed.

  1.  What is the difference between $(window).load and $(document).ready function in jQuery?

Before we go into the differences, let’s first examine why these methods are needed in jQuery.

Suppose you place your JavaScript DOM manipulation code or any code that depends on your DOM elements in the head section of your HTML page. In that case, the code will execute before your DOM is fully loaded, which can result in strange errors, so make sure to wrap your code inside special callbacks that fire only when your DOM is fully loaded.

However, if you add any JavaScript code after the body element, your code will be run once your DOM has been fully loaded, so you don’t need to worry about wrapping your code in any callbacks.

$(document).ready() uses either the modern browser API event DOMContentLoaded to check if your DOM is ready or the readyState document variable to check if the DOM is fully loaded and ready.

Syntax:

$(document).ready(function(){
    //your code here;
});

On the contrary, $(window).load() was designed to verify if the page and its resources are loaded. Resources include images, texts, CSS styles and stylesheets, and JavaScript files; thus, checking if the DOM is ready may be slower.

Syntax:

$(window).load(function(){
    //your code here;
});
  1.  What is jQuery UI?

jQuery UI allows our apps to have an excellent user interface and animation in a more timely manner. It is a collection of plug-ins based on the JavaScript Library, including interface interactions, effects, animations, widgets, and themes. jQuery is used to develop APIs that are coherent and consistent. It is a technique for extending jQuery prototype objects. You can enable all jQuery objects to inherit any method you add by using that prototype object.

Interactions

Interactions may be used to apply simple mouse-based behaviours to any element. The following are some examples of interactions:

  • Draggable
  • Selectable
  • Sortable
  • Droppable
  • Resizable
  1.  What is the use of the html( ) method in jQuery?

To modify the entire content of the selected elements, use the jQuery html() function. It replaces the content of the selected element with new content.

The html() method sets or returns the content (innerHTML) of the selected elements.

When this method is used to return content, it returns the content of the FIRST matched element.

Return Content:

$(selector).html()

When this method is used to set content, it overwrites the content of ALL matching elements.

Set Content:

$(selector).html(content)

Set content using a function:

$(selector).html(function(index,currentcontent))
  • index:- returns the position of the selected element.
  • currentcontent:- returns the current HTML content of the selected element.
  1.  What is the use of the css( ) method in jQuery?

The css() method is used to alter the style property of the selected element. Furthermore, the css() function sets or returns one or more style attributes for the selected elements. 

Return a CSS property

To return the value of the specified element, the below syntax is used:

css("propertyname");

For example:

$("p").css("background-color");

The above example will return the background colour of the paragraph text when an event occurs on the <p> tag.

Set a CSS property:

To set a specified CSS property, use the following syntax:

css("propertyname","value");

For example:

$("p").css("background-color", "yellow");

The above example can be used to make the <p> tag’s background colour yellow.

Set multiple CSS properties:

To set multiple CSS properties, use the following syntax:

css({"propertyname":"value","propertyname":"value",...});

For example:

$("p").css({"background-color": "blue", "font-size": "250%", "border": "3px solid pink"});
  1.  What are events in jQuery? Explain.

User activities on a web page are called events, and responding to such actions is considered event handling.

An event is a precise moment when something occurs.

For examples:

Moving the mouse over an element, selecting a radio button or a checkbox, or clicking on an element. jQuery provides straightforward techniques for adding event handlers to specific elements. When an event happens, the specified function is called.

The syntax for event methods:

Say, to assign a click event to all paragraphs on a page, you can do this:

$("p").click();

The next step is to specify what should happen if the event occurs. You must pass the event as a function.

$("p").click(function(){
  // action goes here!!
});

Assume you want to add a 3px dotted border around the text only when you click :

$("p").click(function(){
  $(this).css({border: "3px dotted black"});
});

The example below shows how the output will look like when you click on the text:

Hey! Click me.
  1.  What is the significance of jQuery.length?

jQuery.length property is used to count the number of elements in a jQuery object.

Syntax:

$(selector).length

For example:

$("button").click(function(){
  alert($("p").length);
});

The above example will return the total count of the <p> element in the document when you click the button.

  1.  What are the selectors in jQuery? How many types of selectors are in jQuery?

To interact with any element on the web page, we must first locate it. In jQuery, selectors are used to finding HTML elements. Some of the most prominent and essential selectors are:

  • Name: It is used to select all elements that match the specified element name.

For example:

$("p")
  • #ID: It is used to select a single element that matches the given ID.

For example:

$("#id")
  • .Class: Used to pick all items that match the specified Class.

For example:

$(".class")
  • The universal (*): Used to select all elements in a DOM. The * selector selects all document elements, including HTML, head, and body. 

Note: Some browsers may struggle to parse the * selector.

For example:

$("*")
  • Multiple Elements E, F, G: These selectors are used to pick the combined results of all the given selectors E, F, or G.

For example:

$("h1, div, p")
  • Attribute Selector: Used to select elements depending on the value of their attributes.

For example:

$("img[alt=quote]")

The list does not finish here; there are numerous extra selectors in jQuery that can be useful when modifying HTML elements.

  1.  Can you provide a brief description of each( ) method in jQuery?

In jQuery, each( ) method specifies a function that is executed for each matching element. It is one of the most often used traversal techniques in JQuery. We can iterate through the DOM elements of the jQuery object using this method and run a function for each matched element.

each( ) receives an argument function(index,element), which is a callback function that executes for each element that is selected. This function further requires two parameters, index and element, which are optional. As a result, we must pass a callback function to each( ) method.

To break the loop early, we can return false from the callback function.

Syntax:

$(selector).each(function(index, element))

For example, suppose you wish to loop across arrays of data and retrieve the index and value of the location of data within the array:

var list = ["Coding", "Ninjas", "is", "a", "great", "platform"];$.each(list, function(index, value){    console.log(index + " "+ value);})

Output

0 Coding1 Ninjas2 is3 a4 great5 platform

In the preceding example, the value of every list element is displayed following its index.

We can also iterate over the objects using each( ) method:

For example:

var obj = {"name": "Ninja","type": "Coder"};$.each(obj, function(key,value){    console.log(key + " - " + value);})

Output

name - Ninjatype - Coder
  1.  Can you elaborate the difference between prop( ) and attr( ) methods?

Both attr() and prop() are used to retrieve or update the value of a given property of an element attribute. However attr() returns the property’s default value (Original state), and prop() returns the current value (Current state).

  • .attr() method changes attributes for specified HTML tags.
  • .prop() method changes properties for specified HTML tag as per the DOM tree.
  • JQuery is a dynamic library that is always being improved. In some cases, the distinction between attributes and properties is critical. Before jQuery 1.6, the .attr() function occasionally considers property values when obtaining some attributes, leading to inconsistency. As of jQuery 1.6, the .prop() function can be used to directly obtain property values, whereas .attr() can be used to retrieve attributes.
  • In the majority of cases, prop() does what attr() used to do.
  1.  Difference between .empty(), .remove() and, .detach() in Jquery ?
  • The empty() function in jQuery eliminates all child nodes and their content for the selected elements.

Syntax:

$(selector).empty()

For example:

$("button").click(function(){  $("div").empty();});
  • In JQuery, the remove() method deletes all selected elements, including the text. This technique also removes any data and events associated with the selected elements.

Syntax:

$(selector).remove(selector)

The parameter selector is optional inside the remove( ) method. It is used to specify one or more elements to be removed. To remove multiple elements, separate them with a comma (,).

For example:

$("button").click(function(){  $("p").remove();});
  • The detach() function in jQuery removes the selected elements from the DOM tree, including all text and child nodes, but maintains the data and events. This method is useful when removed elements are to be reinserted into the DOM at a later time.

Syntax:

$(selector).detach()

For example:

$("button").click(function(){  $("p").detach();});

Points to remember

  • jQuery is widely used:- Because of its simplicity and ease of use, jQuery is quite popular among website developers. When dealing with this popular language, you will never run out of resources, and you will always be able to discover what you need and get all of your questions addressed.
  • Promotes simplicity:- Because the library is created with fewer and shorter codes, most website developers believe jQuery to be easy to learn and intuitive. Developers do not need experienced web designers or programmers to create beautiful designs for their websites with jQuery. Web developers who have done some CSS file testing and coding will enjoy how simple jQuery is to use.
  • Clean and beautiful syntax:- jQuery employs strong, clear, and simple syntax, making it easy to choose the DOM elements on the web page that you want to alter using JavaScript and allowing you to chain effects and actions together for efficient coding. It is standard practice to replace dozens or hundreds of JavaScript lines with a single line of jQuery code. jQuery selects elements using Cascading Style Sheets (CSS) version 3, so you won’t have to learn a new syntax while using this language.

Key takeaways

In this article, we covered the Top 25 Jquery Interview Questions for Beginners. The list does not end here as we have further divided it into two parts, the second of which contains the Advanced level Interview questions asked by the product-based companies. If you want to build your career in development, the questions given above will undoubtedly help you achieve your ideal job.

Ninja, have a great time learning.

By: Alisha Chhabra