Advanced jQuery Questions and Answers Interview

1. What is the difference between $(this) and this in jQuery?

Answer:

• this refers to the current DOM element.

• $(this) converts the DOM element into a jQuery object so you can use jQuery methods.

Example: $("button").click(function(){ console.log(this); // DOM elementconsole.log($(this)); // jQuery object });

2. What is event delegation in jQuery?

Answer:
Event delegation allows attaching an event handler to a parent element to handle events for dynamically added child elements.

It improves performance and works for dynamically created elements.

3. What is the difference between .prop() and .attr()?

Answer:

• .attr() gets/sets HTML attributes.

• .prop() gets/sets DOM properties.

Example:$("#check").prop("checked", true);

Use .prop() for boolean properties like checked, selected, disabled.

4. What is the difference between .empty(), .remove(), and .detach()?

Answer:

• .empty() removes child elements.

• .remove() removes element and its data/events.

• .detach() removes element but keeps data/events for re-use.

5. What is jQuery Deferred Object?

Answer:
Deferred object is used for asynchronous operations like AJAX. It helps manage success, failure, and completion states.

Example: $.ajax("data.json") .done(function(data){ console.log("Success"); }) .fail(function(){ console.log("Error"); });

6. What is the difference between .on(), .bind(), and .live()?

Answer:

• .bind() attaches event directly (older method).

• .live() was used for dynamic elements (deprecated).

• .on() is the modern and recommended method for event handling.

7. How does jQuery handle AJAX requests?

Answer:
Using $.ajax(), $.get(), and $.post() methods.

Example: $.ajax({ url: "server.php", type: "POST", data: {name: "John"}, success: function(response){ console.log(response); } });

8. What is chaining in jQuery? Why is it useful?

Answer:
Chaining allows multiple methods on the same element, reducing code repetition.

It improves readability and performance.

9. How to prevent default action in jQuery?

Answer:Use event.preventDefault().

10. What is the difference between .find() and .children()?

Answer:

• .children() selects direct child elements only.

• .find() selects all descendant elements.

11. What is the use of $.noConflict()?

Answer: It releases the $ symbol so other libraries can use it.

12. What are jQuery Callbacks?

Answer:
Callbacks are functions executed after an action completes.

Example: $("#box").hide("slow", function(){ alert("Hidden"); });

13. What is the difference between .width() and .innerWidth()?

Answer: 

• .width() returns element width without padding.

• .innerWidth() includes padding.

14. How to optimize jQuery performance?

Answer:

• Cache selectors

• Use event delegation

• Minimize DOM manipulation

• Use chaining

• Avoid unnecessary animations

Example:

15. Is jQuery still relevant in 2026?

Answer: Yes, jQuery is still used in many legacy systems and small-to-medium websites. However, modern frameworks like React, Angular, and Vue are preferred for large-scale applications.

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