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IntersectionObserverEntry: intersectionRatio property

The IntersectionObserverEntry interface's read-only intersectionRatio property tells you how much of the target element is currently visible within the root's intersection ratio, as a value between 0.0 and 1.0.

Value

A number between 0.0 and 1.0 which indicates how much of the target element is actually visible within the root's intersection rectangle. More precisely, this value is the ratio of the area of the intersection rectangle (intersectionRect) to the area of the target's bounds rectangle (boundingClientRect).

If the area of the target's bounds rectangle is zero, the returned value is 1 if isIntersecting is true or 0 if not.

Examples

In this simple example, an intersection callback sets each target element's opacity to the intersection ratio of that element with the root.

js

function intersectionCallback(entries) {
  entries.forEach((entry) => {
    entry.target.style.opacity = entry.intersectionRatio;
  });
}

To see a more concrete example, take a look at Handling intersection changes.

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
intersectionRatio 51 15 55 No 38 12.1 51 51 55 41 12.2 5.0

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https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserverEntry/intersectionRatio