jQuery Interview Questions and Answers for freshers

1. What is jQuery?

   • Answer: jQuery is a fast, small, and feature-rich JavaScript library. It simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development.

2. How do you include jQuery in an HTML file?

   • Answer: You can include jQuery using a ``

3. Explain the $() function in jQuery.

   • Answer: The `$()` function is jQuery's core function. It's used to select HTML elements and create jQuery objects. It's essentially a shortcut for `jQuery()`. For example, `$('#myElement')` selects the element with the ID "myElement".

4. What are selectors in jQuery? Give examples.

   • Answer: Selectors are used to select HTML elements. Examples include: `#id` (by ID), `.class` (by class), `element` (by element type), `*` (all elements), `:first`, `:last`, `:even`, `:odd` (filtering), etc.

5. How do you select elements by ID, class, and tag name?

   • Answer: `$("#myId")` selects by ID, `$(".myClass")` selects by class, and `$("p")` selects all paragraph elements.

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

   • Answer: `attr()` gets or sets attributes (like `src`, `href`, `title`), while `prop()` gets or sets properties (like `checked`, `selected`, `disabled`). `prop()` is generally preferred for boolean properties.

7. Explain `text()`, `html()`, and `val()` methods.

   • Answer: `text()` gets or sets the text content of an element; `html()` gets or sets the HTML content; `val()` gets or sets the value of form elements (like input fields).

8. How do you add, remove, and toggle classes with jQuery?

   • Answer: `addClass("myClass")`, `removeClass("myClass")`, `toggleClass("myClass")`.

9. How do you handle events in jQuery? Give examples.

   • Answer: Use methods like `click()`, `mouseover()`, `mouseout()`, `keyup()`, etc. Example: `$("#myButton").click(function(){ alert("Button clicked!"); });`

10. Explain jQuery's `each()` method.

    • Answer: `each()` iterates over a jQuery collection (set of elements), allowing you to perform actions on each element individually.

11. What is the purpose of `append()`, `prepend()`, `after()`, and `before()`?

    • Answer: These methods add content to the DOM. `append()` adds content to the *end* of an element, `prepend()` adds content to the *beginning*, `after()` adds content *after* the element, and `before()` adds content *before* the element.

12. How do you use jQuery to make an AJAX request?

    • Answer: Use the `$.ajax()` method or shorthand methods like `$.get()` and `$.post()`. These methods allow you to send requests to a server and handle the response.

13. Explain the concept of chaining in jQuery.

    • Answer: Chaining allows you to call multiple jQuery methods sequentially on the same jQuery object, making code more concise and readable. Example: `$("#myElement").addClass("active").css("color", "red").show();`

14. What are jQuery effects? Give examples.

    • Answer: jQuery effects provide animation capabilities. Examples include `show()`, `hide()`, `fadeIn()`, `fadeOut()`, `slideUp()`, `slideDown()`, `animate()` (for custom animations).

15. How do you handle events on dynamically added elements?

    • Answer: Use event delegation. Attach the event handler to a parent element that *will* exist when the page loads, and use the `on()` method to listen for events on the dynamically added child elements. The event will bubble up to the parent.

16. What are jQuery plugins?

    • Answer: jQuery plugins are extensions that add new functionality to jQuery. They are essentially functions or objects that extend jQuery's capabilities.

17. How do you create a simple jQuery plugin?

    • Answer: A simple plugin would be a function that takes a jQuery object as input and adds functionality. It's usually added to jQuery's prototype using `$.fn.extend()` or `$.fn. = function(){...}`

18. Explain the concept of Deferred objects in jQuery.

    • Answer: Deferred objects represent asynchronous operations, allowing you to manage callbacks for success and failure, and chain asynchronous actions together using `.then()` and `.fail()` methods.

19. How do you prevent default behavior of an event?

    • Answer: Use `event.preventDefault()` within the event handler function.

20. How do you stop event propagation?

    • Answer: Use `event.stopPropagation()` within the event handler function.

21. What is the difference between `live()` and `on()`?

    • Answer: `live()` is deprecated. `on()` is the preferred method for attaching event handlers, especially for dynamically added elements, due to its efficiency and support for event delegation.

22. Explain how to use jQuery's `map()` method.

    • Answer: The `map()` method transforms a set of elements into a new array by applying a function to each element. It's useful for processing data from a collection.

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