The 20 most common jQuery interview questions and answers

In this article, I’m going to share 20 jQuery questions that HTML and JavaScript developers encounter in different interviews. Some of these questions might also be addressed in Java Web development interviews that require both server-side (Spring, Servlet, and JSP) and client-side (HTML, CSS, JavaScript, and jQuery) development.

If you’re interviewing for a position, it requires you to have multiple skills, such as: Java, jQuery. It doesn’t expect you to understand every nuances and details of jQuery, but if you’re interviewing for a real client development position, you’ll need to accumulate more advanced and skillful jQuery questions than the ones outlined in this article. However, this article is a quick refresher on some of the most frequently asked questions in jQuery interviews, and most of them are applicable to web developers with 2 to 5 years of experience, especially in the Java field.

JQuery interview Questions and answers

JavaScript is the standard language for client-side scripting, and jQuery makes it much easier to write JavaScript. You can do a lot more with just a few lines of jQuery code. It is one of the most used JavaScript libraries, and there are very few new projects that use native JavaScript instead of jQuery. What this means for you as a Java Web developer is that you will find a lot of jQuery interview questions in a Java Web development interview.

In the early days, it was mostly HTTP, HTML, CSS, and JavaScript, but more recently, in addition to JavaScript basics, people want to know if you’re familiar with jQuery. These 16 jQuery questions are for Web developers, and are also handy for correcting key concepts before a phone or video round of interviews. If you are new to jQuery, it will also help you understand the basics better and inspire you to discover more.

1. What is $() in jQuery library? (Answers below)

The $() function is another name for the jQuery() function, which at first glance looks odd and makes the jQuery code obscure. Once you get used to it, you’ll love its simplicity. The $() function is used to wrap any object into a jQuery object, and you are then allowed to call a number of different methods defined on the jQuery object. You can even pass a selector string into the $() function, which returns a jQuery object containing an array of all matched DOM elements. I’ve seen this question come up several times, and although it’s very basic, it’s often used to distinguish whether a developer knows jQuery or not.

2. There are five on the website

Element, how do I select them using jQuery? (the answer)

Another important jQuery issue is selector based. JQuery supports different types of selectors, such as ID selectors, class selectors, and label selectors. Since ID and class are not mentioned in this question, you can use the tag selector to select all div elements. JQuery code: $(“div”), which returns a jQuery object containing all five div tags. See the article linked above for more detailed answers.

3. What is the difference between the ID selector and the class selector in jQuery? (The answer)

If you’ve ever worked with CSS, you probably know the difference between an ID selector and a class selector, and jQuery is no different. ID selectors use IDS to select elements, such as #element1, while class selectors use CSS classes to select elements. Use the ID selector when you only need to select one element, and use the class selector if you want to select a group of elements with the same CSS class. During the interview process, you will most likely be asked to write code using ID and class selectors. The following jQuery code uses the ID selector and the class selector:

$('#LoginTextBox')  // Returns element wrapped as jQuery object with id='LoginTextBox'
$('.active') // Returns all elements with CSS class active.Copy the code

As you can see, another syntactically different difference between the ID selector and the class selector is that the former uses the character “#” while the latter uses the character “. . See the answers link above for more detailed analysis and discussion.

4. How to use jQuery to hide an image when clicking a button?

This is an event handling problem. JQuery provides good support for events like button clicks. You can hide an image by ID or class using the following code. You need to know how to set the event for the button and execute the hide() method as follows:

$('#ButtonToClick').click(function(){
    $('#ImageToHide').hide();
});Copy the code

I like this problem because it’s very practical and the code isn’t complicated.

5. What function is $(document).ready()? Why use it?(answer)

This is an important question and one that is often asked. The ready() function is used to execute code when the document enters the ready state. JQuery allows you to execute code when the DOM is fully loaded (such as when the HTML is fully parsed and the DOM tree is built). The great thing about using $(document).ready() is that it works in all browsers, and jQuery takes the cross-browser issue out of the way. Users who need more information can click the Answer link for a detailed discussion.

6. How is the JavaScript window.onload event different from jQuery Ready? (The answer)

This question and answer follows on from the last one. The main difference between the JavaScript window.onload event and the jQuery Ready function is that the former waits for the DOM to be created and for all external resources, including large images, audio, and video, to be fully loaded. If loading images and media content takes a lot of time, the user will experience significant delays in the execution of the code defined on the window.onload event.

The jQuery Ready () function, on the other hand, only needs to wait for the DOM tree, not for images or external resources to load, making it faster to execute. Another advantage of using jQuery $(document).ready() is that you can use it multiple times in a web page. The browser executes them in the order they appear in the HTML page, as opposed to onLoad, which can only be used in a single function. For this benefit, it is better to use jQuery ready() rather than JavaScript window.onload events.

7. How do I find all the selected items of the HTML SELECT tag? (Answers below)

This is one of the trickier jQuery interview questions. This is a basic question, but don’t expect every jQuery beginner to know it. You can use the following jQuery selector to get all the selected items with multiple=true tags:

$('[name=NameOfSelectedTag] :selected')Copy the code

This code uses a combination of the property selector and the: Selected selector to return only the selected option. You can modify it as needed, such as using the ID attribute instead of the name attribute to get the select tag.

8. What function is each() in jQuery? How do you use it? (Answers below)

The each() function is like an Iterator in Java, allowing you to iterate over a collection of elements. You can pass a function to the each() method, and the called jQuery object will execute the function on each of its elements. Sometimes this problem is followed by the previous one, for example, how to display all selected items in the Alert box. We can use the selector code above to find all the checked items, and then print them one by one using the each() method in the alert box as follows:

$('[name=NameOfSelectedTag] :selected').each(function(selected) {
    alert($(selected).text());
});Copy the code

The text() method returns the text of the option.

9. How do you add an HTML element to a DOM tree? (Answers below)

You can add an HTML element to the DOM tree using the jQuery method appendTo(). This is one of the many ways jQuery provides to manipulate the DOM. You can add an existing element or a new HTML element to the end of the specified DOM element using the appendTo() method.

10. Can you use jQuery code to select all hyperlinks inside paragraphs? (Answer omitted)

This is another jQuery interview question about selectors. Just like any other problem, it only takes one line of jQuery code to solve. You can use the following jQuery code snippet to select all nested paragraphs (

Tag) internal hyperlinks (A tag)……

11. How are the $(this) and this keywords different in jQuery? (Answers below)

This is a tricky problem for many jQuery beginners, but it’s a simple one. $(this) returns a jQuery object on which you can call multiple jQuery methods, such as text() for text, val() for value, and so on. And this represents the current element, which is one of the JavaScript keywords that represents the current DOM element in the context. You cannot call jQuery methods on it until it is wrapped in a $() function, such as $(this).

12. How do you use jQuery to extract the attributes of an HTML tag for example. Href link? (the answer)

The attr() method is used to extract the value of an attribute of any HTML element. You first need to select and select all links or a specific link using jQuery, and then you can apply the attr() method to get their href value. The following code finds all the links in the page and returns the href value:

$('a').each(function(){
   alert($(this).attr('href'));
});Copy the code

13. How do you set a property value using jQuery? (the answer)

An additional follow-up to the previous problem is that the attr() method, like any other in jQuery, has more than one power. If you call attr() with a value like.attr (name, value), name is the genus