Intersection Observer API
This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
The Intersection Observer API provides a way to asynchronously observe changes in the intersection of a target element with an ancestor element or with a top-level document's viewport.
Intersection observer concepts and usage
The Intersection Observer API allows you to configure a callback that is called whenever one item, called a target, intersects either the device viewport or a specified element called, for the purpose of this API, the root element. Create the intersection observer by calling its constructor and passing it a reference to the callback function.
var options = { root: document.querySelector('#scrollArea'), rootMargin: '0px', threshold: 1.0 } var callback = function(entries, observer) { /* Content excerpted, show below */ }; var observer = new IntersectionObserver(callback, options);
A threshold of 1.0 means that when 100 percent of target
is visible within the root
element, the callback is invoked.
Once you have the observer, give it a target.
var target = document.querySelector('#listItem'); observer.observe(target);
Whenever the target meets the threshold specified for the IntersectionObserver, the callback is invoked.
var callback = function(entries, observer) { entries.forEach(entry => { entry.time; // a DOMHightResTimeStamp indicating when the intersection occurred. entry.rootBounds; // a DOMRectReadOnly for the intersection observer's root. entry.boundingClientRect; // a DOMRectReadOnly for the intersection observer's target. entry.intersectionRect; // a DOMRectReadOnly for the visible portion of the intersection observer's target. entry.intersectionRatio; // the number for the ratio of the intersectionRect to the boundingClientRect. entry.target; // the Element whose intersection with the intersection root changed. }); };
Interfaces
IntersectionObserver
- Provides a way to asynchronously observe changes in the intersection of a target element with an ancestor element or with a top-level document's viewport. The ancestor or viewport is referred to as the root.
IntersectionObserverEntry
- Provides information about the intersection of a particular target with the observers root element at a particular time. Instances of this interface cannot be created, but a list of them is returned by
IntersectionObserver.takeRecords()
.
Specifications
Specification | Status | Comment |
---|---|---|
Intersection Observer | Editor's Draft | Initial definition. |
Browser Compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support |
51.0 |
? | ? | ? | ? |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|
Basic support | No support | 51.0 | ? | ? | ? | ? | ? | 51.0 |
See also
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/intersection_observer_api