lazy-load

@stellar-apps/lazy-load

yarn add @stellar-apps/lazy-load

Usage

import LazyLoad, {LazyImage, LazyIframe} from '@stellar-apps/lazy-load'

function LazyVideo ({src, offset = 100, ...props}) {
  return (
    <LazyLoad rootMargin='200px'>
      {({lazyLoadRef, isVisible}) => (
        <video 
          key={String(isVisible)} 
          ref={lazyLoadRef} 
          src={isVisible ? src : ''}
          {...props}
        />               
      )}
    </LazyLoad>
  )
}

LazyLoad

A render props component pattern for lazy loading elements as they appear in the viewport

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

Render props

• lazyLoadRef {React.creatRef}
  • Must be provided as a ref to the underlying element you are lazy loading
• isVisible {boolean}
  • Returns true if the the element has been loaded and false if not.
• visibilityRatio {number}
  • Returns the ratio of the intersectionRect to the boundingClientRect. That is to say, it's the amount of the element that is current visible within the root.

---

LazyImage

Inherits props from HTML <img>, curls/Box and LazyLoad

Props

• rootMargin {string}
  • default 160px
• placeholder(<Object {lazyLoadRef}>) {func}
  • Should return a component to display when the element is not yet visible

---

LazyIframe

Inherits props from HTML <iframe>, curls/Box, and LazyLoad

Props

• rootMargin {string}
  • default 100px
• placeholder(<Object {lazyLoadRef}>) {func}
  • Should return a component to display when the element is not yet visible