intersection-observer-admin

intersection-observer-admin

Why use an administrator to manage all the elements on my page?

This library is used in ember-in-viewport and ember-infinity. This library is particularly important for re-using the IntersectionObserver API.

Most implementations have one Intersection Observer for each target element or so called sentinel. However, IntersectionObserver.observe can observer multiple sentinels. So this library will resuse the IntersectionObserver instance for another element on the page with the same set of observer options and root element. This can dramatically improve performance for pages with lots of elements and observers.

Installation

npm install intersection-observer-admin --save

Usage

API

1. element: DOM Node to observe
2. enterCallback: Function
   • callback function to perform logic in your own application
3. exitCallback: Function
   • callback function to perform when element is leaving the viewport
4. observerOptions: Object
   • list of options to pass to Intersection Observer constructor (https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/IntersectionObserver)
   • scrollableArea: String
     • used for determining if element should use existing or new IntersectionObserver

import IntersectionObserverAdmin from 'intersection-observer-admin';

const intersectionObserverAdmin = new IntersectionObserverAdmin();

// Add callbacks that will be called when observer detects entering and leaving viewport
intersectionObserverAdmin.addEnterCallback(element, enterCallback);
intersectionObserverAdmin.addExitCallback(element, exitCallback);

// add an element to static administrator with window as scrollable area
intersectionObserverAdmin.observe(element, { root, rootMargin: '0px 0px 100px 0px', threshold: 0 });

// add an element in a scrolling container
intersectionObserverAdmin.observe(element, { root, rootMargin: '0px 0px 100px 0px', threshold: 0, scrollableArea: '.my-list' });

// Use in cleanup lifecycle hooks (if applicable) from the element being observed
intersectionObserverAdmin.unobserve(element, observerOptions);

// Use in cleanup lifecycle hooks of your application as a whole
// This will remove the in memory data store holding onto all of the observers
intersectionObserverAdmin.destroy();

IntersectionObserver's Browser Support

Out of the box

Chrome	51 [1]
Firefox (Gecko)	55 [2]
MS Edge	15
Internet Explorer	Not supported
Opera [1]	38
Safari	Safari Technology Preview
Chrome for Android	59
Android Browser	56
Opera Mobile	37

• [1] Reportedly available, it didn't trigger the events on initial load and lacks isIntersecting until later versions.
• [2] This feature was implemented in Gecko 53.0 (Firefox 53.0 / Thunderbird 53.0 / SeaMonkey 2.50) behind the preference dom.IntersectionObserver.enabled.