intersection

@stellar-apps/intersection

A render prop component pattern which provides an interface for the IntersectionObserver API.

The IntersectionObserver interface of 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. The ancestor element or viewport is referred to as the root.

When an IntersectionObserver is created, it's configured to watch for given ratios of visibility within the root. The configuration cannot be changed once the IntersectionObserver is created, so a given observer object is only useful for watching for specific changes in degree of visibility.

Installation

yarn add @stellar-apps/intersection

Usage

import Intersection from '@stellar-apps/intersection'

function IntersectionBox (props) {
  return (
    <Intersection pollInterval={100} thresholds={[0, 0.25]}>
      {({intersectionRef, isIntersecting}) => (
        <Box {...props} ref={intersectionRef}>
          Is intersecting? {String(isIntersecting)}
          Intersection ratio: {String(intersectionRatio)}
        </Box>
      )}
    </Intersection>
  )
}

Intersection

Props

• root {DOM Element}
  • default document
  • A specific ancestor of the target element being observed. If no value was passed to the constructor or this is null, the top-level document's viewport is used
• rootMargin {string}
  • default 0 0 0 0
  • Margin around the root. Can have values similar to the CSS margin property, e.g. "10px 20px 30px 40px" (top, right, bottom, left). The values can be percentages. This set of values serves to grow or shrink each side of the root element's bounding box before computing intersections.
• thresholds {number|Array}
  • default 0
  • Either a single number or an array of numbers which indicate at what percentage of the target's visibility the observer's callback should be executed. If you only want to detect when visibility passes the 50% mark, you can use a value of 0.5. If you want the callback to run every time visibility passes another 25%, you would specify the array [0, 0.25, 0.5, 0.75, 1]. The default is 0 (meaning as soon as even one pixel is visible, the callback will be run). A value of 1.0 means that the threshold isn't considered passed until every pixel is visible.
• pollInterval {number}
  • default null
  • The frequency in which the polyfill polls for intersection changes
  • Only relevant if you'd like to detect changes for any of the following:
    • CSS changes on :hover, :active, or :focus states
    • CSS changes due to transitions or animations with a long initial delay
    • Resizable <textarea> elements that cause other elements to move around
    • Scrolling of non-document elements in browsers that don't support the event capture phase
• disableMutationObserver {bool}
  • default false
  • You can choose to not check for intersections when the DOM changes by setting this property to true
• initialIsIntersecting {bool}
  • default false
  • Changes the default value of isIntersecting for use in places like SSR

Render props

• intersectionRef {React.createRef}
  • Must be provided to the element you'd like to start observing
  • <div ref={intersectionRef}/>
• boundingClientRect {DOMRectReadOnly}
  • default null
  • Returns the bounds rectangle of the target element as a DOMRectReadOnly. The bounds are computed as described in the documentation for Element.getBoundingClientRect().
• intersectionRect {DOMRectReadOnly}
  • default null
  • Returns a DOMRectReadOnly representing the target's visible area
• intersectionRatio {number}
  • default 0
  • Returns the ratio of the intersectionRect to the boundingClientRect
• isIntersecting {bool}
  • default props.initialIsIntersecting
  • A Boolean value which is true if the target element intersects with the intersection observer's root. If this is true, then, the IntersectionObserverEntry describes a transition into a state of intersection; if it's false, then you know the transition is from intersecting to not-intersecting.
• rootBounds {DOMRectReadOnly}
  • default null
  • Returns a DOMRectReadOnly for the intersection observer's root
• target {DOMElement}
  • default null
  • The Element whose intersection with the root changed
• time {DOMHighResTimeStamp}
  • default null
  • A DOMHighResTimeStamp indicating the time at which the intersection was recorded, relative to the IntersectionObserver's time origin.