Top 50 jQuery interview questions and answers with examples:
Other Technical Interview Questions and Answers
1. What is jQuery?
Answer: jQuery is a fast and concise JavaScript library designed to simplify HTML document traversal, event handling, and animation on web pages.
2. How can you include jQuery in an HTML page?
Answer: You can include jQuery by adding the following code inside the <head> section of your HTML document:
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
3. What is the difference between $ and jQuery in jQuery?
Answer: $ is an alias for the jQuery object, and both can be used interchangeably. $ is often used because it's shorter and more convenient.
4. How do you select elements with a class in jQuery?
Answer: You can select elements with a class using the $(".classname") selector. For example:
$(".myClass").addClass("highlight");
5. Explain the difference between $(document).ready() and $(window).load() in jQuery.
Answer: $(document).ready() fires when the DOM is fully loaded, while $(window).load() fires when all assets (images, etc.) have finished loading. Use $(document).ready() for most operations to improve page load performance.
6. How can you bind an event in jQuery?
Answer: You can use the .on() method to bind events. For example:
$("#myButton").on("click", function() {
// Your code here
});
7. Explain event delegation in jQuery.
Answer: Event delegation allows you to attach a single event handler to a common ancestor of multiple elements instead of attaching handlers to each element individually. This is more efficient. Example:
javascript
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$("#container").on("click", "button", function() {
// Handle button click
});
8. How do you make an AJAX request in jQuery?
Answer: You can use the $.ajax() method to make AJAX requests. For example:
javascript
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$.ajax({
url: "example.com/api",
method: "GET",
success: function(data) {
// Handle the response
},
error: function(xhr, status, error) {
// Handle errors
}
});
9. Explain the difference between $.get() and $.post() in jQuery.
Answer: $.get() is used for making GET requests, while $.post() is used for making POST requests. $.get() appends data to the URL, while $.post() sends data in the request body.
10. How can you animate an element in jQuery?
- Answer: You can use the .animate() method to animate elements. For example:
javascript $("#myElement").animate({ left: '250px' }, 1000);
11. What is method chaining in jQuery?
- Answer: Method chaining is a technique where you can call multiple jQuery methods on the same element in a single statement. Example:
javascript $("#myElement").addClass("highlight").fadeOut(1000);
12. How do you stop an ongoing animation in jQuery?
- Answer: You can use the .stop() method to stop an ongoing animation. Example:
javascript $("#myElement").stop();
13. What is the difference between .html() and .text() in jQuery?
- Answer: .html() sets or gets the HTML content of an element, while .text() sets or gets the text content, stripping any HTML tags.
14. How do you select the first and last elements in a list using jQuery?
- Answer: You can use the :first and :last selectors. For example:
javascript $("ul li:first").css("color", "red"); $("ul li:last").css("color", "blue");
15. What is the use of the .each() method in jQuery?
- Answer: The .each() method iterates over a jQuery object, executing a function for each element in the collection. Example:
javascript $("li").each(function(index) { console.log(index + ": " + $(this).text()); });
16. How do you set and get attributes in jQuery?
- Answer: You can use the .attr() method to set and get attributes. Example:
```javascript
// Set an attribute
$("#myElement").attr("href", "https://example.com");
javascript
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// Get an attribute
var hrefValue = $("#myElement").attr("href");
```
17. What is event propagation in jQuery, and how do you stop it?
- Answer: Event propagation refers to the order in which events are triggered when an event occurs on an element. You can stop event propagation using the .stopPropagation() method:
javascript $("#childElement").click(function(event) { event.stopPropagation(); });
18. How do you hide and show elements in jQuery?
- Answer: You can use the .hide() and .show() methods. Example:
javascript $("#myElement").hide(); $("#myElement").show();
19. What is the purpose of the $.noConflict() method in jQuery?
- Answer: $.noConflict() releases the $ variable so it can be used by other libraries that may also use it. You can use jQuery instead of $ after calling $.noConflict().
20. How do you check if an element exists in jQuery?
- Answer: You can use the .length property to check if an element exists. Example:
javascript if ($("#myElement").length > 0) { // Element exists }
21. How do you add and remove classes in jQuery?
- Answer: You can use the .addClass() and .removeClass() methods. Example:
javascript $("#myElement").addClass("highlight"); $("#myElement").removeClass("highlight");
22. What is the $.each() function in jQuery, and how does it differ from .each()?
- Answer: $.each() is a utility function that can iterate over both arrays and objects, while .each() is a jQuery method specifically designed for iterating over jQuery collections.
23. How can you delay code execution in jQuery?
- Answer: You can use the setTimeout() function to introduce a delay. For example:
javascript setTimeout(function() { // Code to execute after a delay }, 1000); // 1000 milliseconds (1 second) delay
24. Explain the $.getJSON() method in jQuery.
- Answer: $.getJSON() is a shorthand method for making JSONP or AJAX requests to fetch JSON data. Example:
javascript $.getJSON("data.json", function(data) { // Handle JSON data });
25. What is the purpose of the .empty() method in jQuery?
- Answer: The .empty() method is used to remove all child elements and content from a selected element. Example:
javascript $("#myElement").empty();
26. How can you change the CSS properties of an element using jQuery?
- Answer: You can use the .css() method to change CSS properties. Example:
javascript $("#myElement").css("color", "red");
27. Explain the difference between .append() and .prepend() in jQuery.
- Answer: .append() adds content to the end of the selected element, while .prepend() adds content to the beginning.
28. How do you set and get the value of form elements using jQuery?
- Answer: You can use the .val() method to set and get the value of form elements. Example:
```javascript
// Set value
$("#myInput").val("New Value");
// Get value
var value = $("#myInput").val();
```
29. What is the purpose of the .serialize() method in jQuery?
- Answer: The .serialize() method serializes form data into a URL-encoded string for easy submission via AJAX. Example:
javascript var formData = $("#myForm").serialize();
30. How can you make an element draggable using jQuery UI?
- Answer: You can use the jQuery UI draggable method. Example:
javascript $("#myElement").draggable();
31. What is the difference between $(window).resize() and $(document).ready() in jQuery?
- Answer: $(window).resize() is an event that fires when the browser window is resized, while $(document).ready() fires when the DOM is ready.
32. How do you stop the page from submitting when a form is submitted using jQuery?
- Answer: You can use the .preventDefault() method to stop the default form submission behavior. Example:
javascript $("#myForm").submit(function(event) { event.preventDefault(); // Your code here });
33. Explain the purpose of the .fadeOut() and .fadeIn() methods in jQuery.
- Answer: .fadeOut() hides an element by gradually reducing its opacity, while .fadeIn() shows an element by gradually increasing its opacity.
34. How do you make an AJAX request in jQuery with JSON data?
- Answer: You can use the $.ajax() method with the dataType option set to "json". Example:
javascript $.ajax({ url: "example.com/api", method: "POST", data: JSON.stringify({ key: "value" }), dataType: "json", success: function(data) { // Handle JSON response }, error: function(xhr, status, error) { // Handle errors } });
35. What is the purpose of the .remove() method in jQuery?
- Answer: The .remove() method is used to remove selected elements and their descendants from the DOM. Example:
javascript $("#myElement").remove();
36. How do you change the text of an element in jQuery?
- Answer: You can use the .text() method to set or get the text content of an element. Example:
javascript $("#myElement").text("New Text");
37. How can you handle AJAX errors in jQuery?
- Answer: You can use the error callback in the $.ajax() method to handle AJAX errors. Example:
javascript $.ajax({ // ... other options ... error: function(xhr, status, error) { console.error("AJAX error: " + error); } });
38. Explain the difference between .prop() and .attr() in jQuery.
- Answer: .prop() is used to get or set properties of DOM elements, while .attr() is used for HTML attributes. Use .prop() for properties like checked and .attr() for attributes like data-*.
39. How do you create a new element in jQuery and append it to the DOM?
- Answer: You can create a new element using $("<element>") and append it to the DOM using .append() or .appendTo(). Example:
javascript $("<div>New Element</div>").appendTo("#container");
40. What is event delegation, and why is it useful in jQuery?
- Answer: Event delegation is a technique where you attach a single event listener to a common ancestor of multiple elements and handle events for those elements. It is useful for improving performance when dealing with a large number of elements.
41. How do you check if a checkbox is checked in jQuery?
- Answer: You can use the .prop() method to check if a checkbox is checked. Example:
javascript if ($("#myCheckbox").prop("checked")) { // Checkbox is checked }
42. What is the purpose of the .slideUp() and .slideDown() methods in jQuery?
- Answer: .slideUp() hides an element by gradually reducing its height, while .slideDown() shows an element by gradually increasing its height.
43. How can you add and remove elements from an array using jQuery?
- Answer: You can use JavaScript methods like .push() to add elements to an array and .splice() to remove elements. jQuery does not have specific methods for this.
44. What is the .closest() method in jQuery used for?
- Answer: The .closest() method is used to find the nearest ancestor that matches a given selector. Example:
javascript var parent = $("#myElement").closest(".container");
45. How can you stop an event from bubbling up in jQuery?
- Answer: You can use the event.stopPropagation() method to stop an event from bubbling up the DOM tree. Example:
javascript $("#childElement").click(function(event) { event.stopPropagation(); });
46. What is the purpose of the .one() method in jQuery?
- Answer: The .one() method attaches an event handler that will only be executed once for a given event on an element.
47. How do you add and remove table rows in jQuery?
- Answer: You can use the .append() and .remove() methods to add and remove table rows, respectively.
48. What is method chaining in jQuery, and why is it useful?
- Answer: Method chaining is a technique where you can call multiple jQuery methods on the same element
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