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Document: scroll event

The scroll event fires when the document view has been scrolled. For element scrolling, see Element: scroll event.

Bubbles Yes
Cancelable No
Interface Event
Event handler property onscroll

Note: In iOS UIWebViews, scroll events are not fired while scrolling is taking place; they are only fired after the scrolling has completed. See Bootstrap issue #16202. Safari and WKWebViews are not affected by this bug.

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 thescroll event for requestAnimationFrame.

// Reference: http://www.html5rocks.com/en/tutorials/speed/animations/

let lastKnownScrollPosition = 0;
let ticking = false;

function doSomething(scrollPos) {
  // Do something with the scroll position
}

document.addEventListener('scroll', function(e) {
  lastKnownScrollPosition = window.scrollY;

  if (!ticking) {
    window.requestAnimationFrame(function() {
      doSomething(lastKnownScrollPosition);
      ticking = false;
    });

    ticking = true;
  }
});

See more, similar examples on the resize event page.

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
1
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