Top jQuery Interview Questions and Answers (2025)

Hirely

at 06 Jan, 2025

Question: Explain the `.animate()` function in jQuery.

Answer:

The .animate() function in jQuery is used to create custom animations on CSS properties of elements. It allows you to animate various properties, such as width, height, opacity, margin, padding, and more. The .animate() method enables the creation of smooth transitions, providing a way to modify an element’s CSS properties over a specified duration.

Syntax:

$(selector).animate(properties, duration, easing, callback);

Parameters:

properties (object) - A set of CSS properties that you want to animate. This object defines the final values for the properties. The properties you can animate include numerical values, such as width, height, opacity, and position, but not all CSS properties are animatable.
duration (string or number) - The duration of the animation, either in milliseconds (e.g., 500 for 500 milliseconds) or a string representing one of the predefined speeds ("slow", "fast").
easing (string) - An optional parameter that specifies the easing function to be used for the animation. Common easing functions are:
- "linear": The animation has a constant speed throughout.
- "swing": The animation starts slow, accelerates in the middle, and then slows down towards the end.
callback (function) - An optional function that is called once the animation is complete. This function will execute once the animation ends.

Example:

<!DOCTYPE html>
<html>
<head>
  <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
  <style>
    #box {
      width: 100px;
      height: 100px;
      background-color: red;
      margin: 20px;
    }
  </style>
</head>
<body>
  <div id="box"></div>

  <script>
    $(document).ready(function() {
      // Animate the #box element
      $('#box').click(function() {
        $(this).animate({
          width: '200px',      // Change width to 200px
          height: '200px',     // Change height to 200px
          opacity: 0.5         // Change opacity to 0.5
        }, 1000, 'swing', function() {
          // Callback function after the animation ends
          alert('Animation Complete!');
        });
      });
    });
  </script>
</body>
</html>

In this example:

When the user clicks on the #box element, the .animate() function is triggered.
The box will animate from its current size to 200px width, 200px height, and opacity of 0.5 over 1 second (1000 milliseconds).
After the animation is complete, the callback function will display an alert: “Animation Complete!”.

Important Notes:

CSS Properties: Only certain CSS properties can be animated. These properties must be numeric values, such as width, height, opacity, top, left, margin, padding, and font-size. Properties like background-color cannot be animated directly, but can be handled with plugins or CSS transitions.
Chaining: You can chain multiple .animate() calls or other jQuery methods to create more complex animations. However, if you want to animate several properties simultaneously, they should all be defined within a single .animate() call.

Example of chaining:
```
$('#box').animate({
  width: '200px'
}).animate({
  height: '200px'
});
```
Animation Queue: jQuery queues animations, meaning if you trigger multiple animations on the same element, they will occur in sequence. You can control this behavior with methods like .queue(), .dequeue(), or .stop().
Stopping Animations: You can stop an animation before it finishes using the .stop() method. This will stop the currently running animation and clear the animation queue for that element.

Example of Chaining and Queue Control:

$('#box')
  .animate({
    width: '200px'
  }, 1000)
  .animate({
    height: '200px'
  }, 1000)
  .fadeOut(500);  // Fade out after animations are complete

In this example:

The box will first animate its width to 200px over 1 second.
Then, it will animate its height to 200px over another second.
Finally, it will fade out in 500 milliseconds after the animations.

Conclusion:

The .animate() function in jQuery is a powerful tool for creating custom animations by smoothly transitioning the CSS properties of an element over a specified time. With optional parameters for duration, easing, and callbacks, it gives developers great flexibility to enhance the user experience with animated effects.

Question: What are jQuery selectors?

Answer:

jQuery selectors are used to select HTML elements in the document so that you can manipulate them using jQuery methods. They are the foundation of any jQuery operation, as you need to select an element first before applying actions like modifying its content, changing its style, binding events, etc.

jQuery selectors are similar to CSS selectors but with additional features and options for traversing the DOM (Document Object Model).

Types of jQuery Selectors:

1. Basic Selectors:

These selectors select elements based on their tag name, class, or id.

ID Selector (#): Selects an element with a specific ID.

$('#elementID') // Selects the element with ID 'elementID'

Class Selector (.): Selects all elements with a specific class.

$('.className') // Selects all elements with class 'className'

Element Selector (Tag Name): Selects all elements of a specific tag type.

$('div') // Selects all <div> elements
$('p')   // Selects all <p> elements

2. Attribute Selectors:

These selectors target elements based on their attributes.

Select elements with a specific attribute:

$('input[type="text"]') // Selects all <input> elements with type 'text'

Select elements with a specific attribute and value:

$('a[href="https://www.example.com"]') // Selects <a> elements with a specific href value

Select elements with any attribute:

$('a[title]') // Selects all <a> elements with a 'title' attribute

3. **Universal Selector (`*`)**:

The universal selector selects all elements in the document.

$('*') // Selects all elements in the document

4. Descendant Selector (`space`):

Selects all elements that are descendants of a specific element.

$('div p') // Selects all <p> elements inside <div> elements

5. Child Selector (`>`):

Selects all direct child elements of a specified element.

$('div > p') // Selects all <p> elements that are direct children of <div>

6. Adjacent Sibling Selector (`+`):

Selects the element that is immediately preceded by a specific element.

$('h2 + p') // Selects the first <p> element immediately following an <h2>

7. General Sibling Selector (`~`):

Selects all elements that are siblings of a specified element.

$('h2 ~ p') // Selects all <p> elements that are siblings of an <h2>

8. Pseudo-classes:

jQuery supports many CSS pseudo-classes for selecting elements in specific states.

:first: Selects the first element in a set.

$('p:first') // Selects the first <p> element

:last: Selects the last element in a set.

$('li:last') // Selects the last <li> element

:even: Selects even-indexed elements (0, 2, 4, …).
```
$('li:even') // Selects even <li> elements
```
:odd: Selects odd-indexed elements (1, 3, 5, …).
```
$('li:odd') // Selects odd <li> elements
```

:eq(): Selects the element at the specified index.

$('li:eq(2)') // Selects the third <li> element (index starts from 0)

:not(): Selects elements that do not match the given selector.

$('p:not(.className)') // Selects all <p> elements that do not have class 'className'

9. Form Selectors:

jQuery provides selectors specifically for form elements.

:input: Selects all input elements (including <input>, <textarea>, <button>, etc.).
```
$(':input') // Selects all input elements
```

:text: Selects all text input elements.

$(':text') // Selects all <input> elements with type='text'

:checked: Selects all checked form elements (checkboxes, radio buttons).
```
$(':checked') // Selects all checked <input> elements
```

:enabled: Selects all enabled form elements.

$(':enabled') // Selects all enabled form elements

:disabled: Selects all disabled form elements.

$(':disabled') // Selects all disabled form elements

10. jQuery-specific Selectors:

:hidden: Selects all hidden elements.

$(':hidden') // Selects all hidden elements

:visible: Selects all visible elements.

$(':visible') // Selects all visible elements

Examples of jQuery Selectors in Action:

Select an element by ID and change its text:
```
$('#elementID').text('New Text');
```
Select all elements with a specific class and apply styles:
```
$('.highlight').css('background-color', 'yellow');
```

Select form input elements that are checked:

$('input:checked').each(function() {
  console.log($(this).val()); // Log the value of each checked input
});

Select the first <p> element and add a class:
```
$('p:first').addClass('first-paragraph');
```

Select elements that are not a certain class:

$('div:not(.excluded)').css('border', '1px solid red');

Conclusion:

jQuery selectors are an essential feature for interacting with HTML elements on a page. They provide a powerful way to select and manipulate elements based on various attributes, classes, IDs, and states. By leveraging CSS selectors and jQuery’s extended capabilities, developers can efficiently manipulate the DOM and create dynamic user interfaces.

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Top jQuery Interview Questions and Answers (2025)

Question: Explain the `.animate()` function in jQuery.

Answer:

Syntax:

Parameters:

Example:

Important Notes:

Example of Chaining and Queue Control:

Conclusion:

Question: What are jQuery selectors?

Answer:

Types of jQuery Selectors:

1. Basic Selectors:

2. Attribute Selectors:

3. **Universal Selector (`*`)**:

4. Descendant Selector (`space`):

5. Child Selector (`>`):

6. Adjacent Sibling Selector (`+`):

7. General Sibling Selector (`~`):

8. Pseudo-classes:

9. Form Selectors:

10. jQuery-specific Selectors:

Examples of jQuery Selectors in Action:

Conclusion:

Read More

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Top jQuery Interview Questions and Answers (2025)

Question: Explain the .animate() function in jQuery.

Answer:

Syntax:

Parameters:

Example:

Important Notes:

Example of Chaining and Queue Control:

Conclusion:

Question: What are jQuery selectors?

Answer:

Types of jQuery Selectors:

1. Basic Selectors:

2. Attribute Selectors:

3. Universal Selector (*):

4. Descendant Selector (space):

5. Child Selector (>):

6. Adjacent Sibling Selector (+):

7. General Sibling Selector (~):

8. Pseudo-classes:

9. Form Selectors:

10. jQuery-specific Selectors:

Examples of jQuery Selectors in Action:

Conclusion:

Read More

Tags

Share

Related Posts

Most Frequently asked amazon-web-services Interview Questions (2024)

Most Frequently asked algorithm Interview Questions (2024)

Most Frequently asked azure Interview Questions (2024)

Trace Job opportunities

Question: Explain the `.animate()` function in jQuery.

3. **Universal Selector (`*`)**:

4. Descendant Selector (`space`):

5. Child Selector (`>`):

6. Adjacent Sibling Selector (`+`):

7. General Sibling Selector (`~`):