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) => {};

A generic 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 requestAnimationFrame.

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;
  }
});

• Document: scrollend event
• Element: scroll event
• Element: scrollend event