Top jQuery Interview Questions and Answers for 2025

author image Hirely
at 06 Jan, 2025
  • Software Development
  • Questions

    • Question: What is jQuery?

    Answer:

    jQuery is a fast, small, and feature-rich JavaScript library designed to simplify the process of writing JavaScript code for web development. It provides an easy-to-use API (Application Programming Interface) that works across a variety of web browsers, enabling developers to manipulate HTML documents, handle events, animate elements, and perform Ajax requests with minimal code.

    Key Features of jQuery:

    1. DOM Manipulation: jQuery makes it easy to select, manipulate, and modify elements in the HTML DOM. You can modify the content, structure, and styling of HTML elements with just a few lines of code.

      Example:

      // Change the text of an element with id 'myDiv'
$('#myDiv').text('New Text Content');

    2. Event Handling: jQuery provides a simple way to handle events like clicks, hover, keypress, and more. You can bind event listeners to DOM elements without worrying about browser compatibility.

      Example:

      $('#myButton').click(function() {
    alert('Button clicked!');
});

    3. Cross-browser Compatibility: One of the major reasons developers use jQuery is that it abstracts away the differences between web browsers (like Chrome, Firefox, IE, etc.). It provides a unified interface for manipulating the DOM, handling events, and performing AJAX requests that work consistently across all browsers.

    4. AJAX Support: jQuery simplifies making asynchronous HTTP requests, such as fetching data from a server without reloading the page. This allows for the creation of dynamic, interactive web pages.

      Example:

      $.ajax({
    url: 'data.json',
    type: 'GET',
    success: function(data) {
        console.log(data);
    }
});

    5. Animation and Effects: jQuery includes a set of built-in animations and effects that can be used to create smooth transitions and interactive UI elements like hiding, showing, fading, and sliding.

      Example:

      $('#myDiv').fadeOut();

    6. Simplified Syntax: jQuery uses a concise syntax that helps developers write less code to accomplish common tasks. Its most well-known feature is the use of the dollar sign ($) to quickly select DOM elements and apply actions.

      Example:

      // Select all <p> elements and hide them
$('p').hide();

    7. Plugin Support: jQuery supports a large ecosystem of plugins that extend its functionality. Developers can easily integrate pre-built plugins for common tasks like image carousels, date pickers, and more.

    Example: Basic Usage of jQuery

    <!DOCTYPE html>
<html>
<head>
    <title>jQuery Example</title>
    <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
    <script>
        $(document).ready(function() {
            // Change content of a div when a button is clicked
            $('#myButton').click(function() {
                $('#myDiv').text('Hello, jQuery!');
            });
        });
    </script>
</head>
<body>
    <button id="myButton">Click me</button>
    <div id="myDiv">Initial Text</div>
</body>
</html>

    In the example above:

    • We included the jQuery library using a CDN (Content Delivery Network).
    • When the button is clicked, the text inside the <div> with the ID myDiv is changed using jQuery’s .text() method.

    Why Use jQuery?

    • Simplified Code: jQuery drastically reduces the amount of code needed to achieve common tasks.
    • Cross-Browser Compatibility: jQuery handles differences between browsers, which can be complex to deal with using plain JavaScript.
    • Extensive Plugin Ecosystem: jQuery has a large number of plugins available to quickly implement advanced features without reinventing the wheel.
    • Asynchronous Support (AJAX): jQuery makes it easy to make asynchronous HTTP requests, enabling dynamic content updates without page reloads.

    Is jQuery Still Relevant?

    While jQuery was once a go-to tool for handling JavaScript on websites, its usage has decreased in recent years with the rise of modern JavaScript frameworks like React, Angular, and Vue.js, which provide more powerful solutions for building complex user interfaces and managing state.

    However, jQuery is still widely used in many existing websites and projects, especially for simpler tasks, legacy projects, or situations where quick development is required.

    Conclusion:

    jQuery is a JavaScript library that simplifies web development by offering a more accessible way to work with the DOM, handle events, perform AJAX requests, and create animations. It reduces the amount of code required to achieve these tasks, promotes cross-browser compatibility, and is still commonly used in many websites today.

    Question: What is the difference between .hide() and .fadeOut() in jQuery?

    Answer:

    Both .hide() and .fadeOut() are jQuery methods used to hide elements, but they work in different ways:

    1. .hide() Method:

    • Purpose: The .hide() method simply hides the selected element(s) by setting their display CSS property to none.
    • Behavior: It instantly hides the element(s) without any animation or visual effect.
    • Use Case: It’s used when you want to hide an element immediately without any transition or fading effect.

    Example:

    $('#myElement').hide();  // Hides the element instantly

    2. .fadeOut() Method:

    • Purpose: The .fadeOut() method gradually fades out the selected element(s) by animating the opacity property from 1 (fully visible) to 0 (invisible) over a period of time.
    • Behavior: It includes a fade-out effect, making the element slowly disappear.
    • Use Case: It’s used when you want to hide an element with a smooth fading transition rather than an instant disappearance.

    Example:

    $('#myElement').fadeOut(1000);  // Fades out the element over 1 second
    • Optional Speed Argument: You can specify the duration of the fade effect (in milliseconds), such as 1000 for 1 second, or use predefined values like fast or slow.
    • Callback: You can also provide a callback function to execute after the fading is complete.

    Example with Callback:

    $('#myElement').fadeOut(1000, function() {
    alert('Element has faded out!');
});

    Key Differences:

    • Animation:

      • .hide() hides the element instantly, without animation.
      • .fadeOut() animates the element by gradually decreasing its opacity.

    • CSS Effect:

      • .hide() only affects the display property, making the element not take up space in the layout.
      • .fadeOut() affects the opacity property, making the element invisible, but it still occupies space in the layout during the fade effect (until fully hidden).

    • Use Cases:

      • Use .hide() when you want to hide an element immediately without any effect.
      • Use .fadeOut() when you want a smooth fading effect before the element is hidden.

    Conclusion:

    • .hide() is used for hiding elements instantly, whereas .fadeOut() is used for hiding elements with a smooth fade-out effect.

    Read More

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