Handle the scroll top event of data list in c năm 2024

The scroll event fires when the document view has been scrolled. To detect when scrolling has completed, see the Document: scrollend event. For element scrolling, see Element: scroll event.

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("scroll", (event) => {});
onscroll = (event) => {};

Since scroll events can fire at a high rate, the event handler shouldn't execute computationally expensive operations such as DOM modifications. Instead, it is recommended to throttle the event using requestAnimationFrame(), setTimeout(), or a CustomEvent, as follows.

Note, however, that input events and animation frames are fired at about the same rate, and therefore the optimization below is often unnecessary. This example optimizes the scroll event for

let lastKnownScrollPosition = 0;
let ticking = false;
function doSomething(scrollPos) {
  // Do something with the scroll position
}
document.addEventListener("scroll", (event) => {
  lastKnownScrollPosition = window.scrollY;
  if (!ticking) {
    window.requestAnimationFrame(() => {
      doSomething(lastKnownScrollPosition);
      ticking = false;
    });
    ticking = true;
  }
});

1.

Description: Get the current vertical position of the scroll bar for the first element in the set of matched elements or set the vertical position of the scroll bar for every matched element.

• version added: 1.2.6

  • This method does not accept any arguments.

The vertical scroll position is the same as the number of pixels that are hidden from view above the scrollable area. Setting the scrollTop positions the vertical scroll of each matched element.

Introduction: Scrolling is a fundamental interaction on the web, and understanding how to handle scroll events can enhance the user experience and enable powerful features in your JavaScript applications. In this blog post, we will explore the window scroll events and learn how to use them effectively in JavaScript with practical examples.

Table of Contents: 1. What are Window Scroll Events? 2. Detecting Window Scroll Events 3. Handling Scroll Event Callbacks 4. Implementing Scroll-based Features — Sticky Navigation Bar — Lazy Loading Images — Infinite Scroll 5. Performance Considerations 6. Cross-browser Compatibility 7. Conclusion

1. What are Window Scroll Events? When a user scrolls a web page, the browser triggers scroll events to notify JavaScript code about the scrolling activity. These events provide valuable information such as the current scroll position, direction, and velocity. By listening to these events, you can create dynamic and interactive web experiences.

2. Detecting Window Scroll Events: In JavaScript, you can attach event listeners to the `window` object to detect scroll events. The most commonly used event is the `scroll` event, which fires whenever the user scrolls the page.

Example:

window.addEventListener('scroll', function(event) { // Your code here });

3. Handling Scroll Event Callbacks: When a scroll event occurs, the registered callback function will be executed. Within this function, you can access properties like `window.scrollY` to get the vertical scroll position. You can perform various actions based on this information, such as updating the UI, triggering animations, or loading additional content.

Example:

window.addEventListener('scroll', function(event) { // Get the current scroll position const scrollPosition = window.scrollY;

// Perform actions based on the scroll position // … });

4. Implementing Scroll-based Features: Scroll events open up a wide range of possibilities for enhancing your web applications. Let’s explore a few examples:

Sticky Navigation Bar:

window.addEventListener('scroll', function(event) { const navigationBar = document.getElementById('navbar');

if (window.scrollY > 200) { navigationBar.classList.add('sticky'); } else { navigationBar.classList.remove('sticky'); } });

Lazy Loading Images:

window.addEventListener('scroll', function(event) { const images = document.querySelectorAll('img[data-src]');

images.forEach(function(image) { if (image.getBoundingClientRect().top < window.innerHeight) { image.src = image.dataset.src; image.removeAttribute('data-src'); } }); });

Infinite Scroll:

window.addEventListener('scroll', function(event) { if (window.innerHeight + window.scrollY >= document.body.offsetHeight) { // Load more content } });

5. Performance Considerations: Scroll events can be triggered frequently during rapid scrolling, which may lead to performance issues if not handled properly. To optimize performance, consider using techniques like debouncing or throttling to limit the frequency of function calls during scroll events.

6. Cross-browser Compatibility: When working with scroll events, it’s essential to ensure cross-browser compatibility. Different browsers may handle scroll events differently, so it’s important to test your code across multiple browsers and consider using a library like `lodash` or a polyfill if needed.

7. Conclusion: Window scroll events are a powerful tool in your JavaScript arsenal, enabling you to create dynamic and interactive web experiences. By understanding how to detect and handle scroll events, you can implement various scroll-based features and improve the overall user experience of your web applications.

Remember to handle scroll events efficiently, optimize for performance, and ensure cross-browser

How do you handle a scroll event?

The better ways to handle the scroll events.

First, set the scrolling flag to false . If the scroll event fires set the scrolling flag to true inside the scroll event handler..

Then, execute the scroll event handler using the setInterval() every 300 milliseconds if the scroll events have been fired..

How do you listen to a scroll?

There are two ways we can listen for it; To listen to a scroll event, you first have to scroll up and down your browser. If you go back to the browser, you will see all those tags, which will now give us a scroll bar. As you can see we have a scroll bar now and we can scroll up and down the page.

What is the event scroll on an element?

The scroll event is sent to an element when the user scrolls to a different place in the element. It applies to window objects, but also to scrollable frames and elements with the overflow CSS property set to scroll (or auto when the element's explicit height or width is less than the height or width of its contents).

How to track scroll event in javascript?

You can use the scroll event triggered by the div and attach an event listener with addEventListener(). Here is an example that dynamically adds more items to a list when the user scrolls to the bottom. To detect when the user reaches the bottom, use scrollHeight - scrollTop === clientHeight .