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Document: scroll event

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.

Syntax

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

js

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

onscroll = (event) => {};

Event type

A generic Event.

Examples

Scroll event throttling

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.

js

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;
  }
});

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
scroll_event 1 12 6 9 11.6 2 4.4 18 6 12 1 1.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/Document/scroll_event