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    react-lazily-img

    1.0.71 • Public • Published

    React Lazily IMG

    React Lazily IMG is a React Wrapper Component to lazily load images. The goal is to use the convenient and known standard HTML tags and just have them lazily loaded.

    Features

    • Picture tag and IMG srcset support
    • Webp detection
    • Placeholder
    • HTML && CSS image support
    • First render when image is downloaded
    • Customize percentage of visibility
    • Custom Callback when image is rendered

    Installation

    npm install react-lazily-img --save

    Demo

    Coming soon.

    How does it work ?

    React Lazily IMG is powered by the performant Intersection Observer API. No need of annoying unperformant scroll event listeners and elem.getBoundingClientRect() to check if an element is in the viewport.

    MDN:

    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.

    Documentation

    Code examples

    Picture tag

    import React from 'react';
     
    // import React Lazily IMG
    import Lazy from 'react-lazily-img';
     
    // import images
    import Image1 from './images/1.jpg';
    import Image1WebP from './images/1.webp';
     
    import Image2 from './images/2.jpg';
    import Image2WebP from './images/2.webp';
     
    import Image3 from './images/3.jpg';
    import Image3WebP from './images/3.webp';
     
    import Placeholder from './images/placeholder.jpg';
    import PlaceholderWebp from './images/placeholder.webp';
     
    // You dont need to set webp to true when working with a picture tag as its has a webp detection on its own. 
     
    const options = {
      waitComplete: false, 
      webp: false
    };
     
    const App (props) => (
      <div className="App">
        <Lazy {...options}>
          <picture>
            <source type="image/webp" media="(min-width:600px)" data-srcset={Image1WebP} />
            <source type="image/webp" media="(min-width:500px)" data-srcset={Image2WebP} />
            <source media="(min-width:600px)" data-srcset={Image1} />
            <source media="(min-width:500px)" data-srcset={Image2} />
            <img data-src={Image3} data-webpsrc={Image3WebP} alt="butterfly" />
          </picture>
        </Lazy>
      </div>
    );

    IMG srcset

    <Lazy {...options}>
      <img 
        data-srcset={`
          ${Image1} 320w,
          ${Image3} 480w,
          ${Image2} 800w`}
        data-webpsrcset={`
          ${Image1WebP} 320w,
          ${Image3WebP} 480w,
          ${Image2WebP} 800w`}
        sizes="
          (max-width: 320px) 280px,
          (max-width: 480px) 440px,
          800px"
        alt="butterfly"
        data-src={Image1}
        data-webpsrc={Image1WebP}
      /> 
    </Lazy>

    IMG tag

    <Lazy {...options}>
      // data-webpsrc and the optional data-webpplaceholder are only needed 
      // if you enable webp detection in the options
     
      // placeholder are optional. Image that is shown until the image is in the viewport
     
      <img data-placeholder={Placeholder} data-webpplaceholder={PlaceholderWebp} data-src={Image1} data-webpsrc={Image1WebP} alt="butterfly" />
    </Lazy>

    DIV tag - CSS background

    <Lazy {...options}>
      <div data-src={Image1} data-webpsrc={Image1WebP} />
    </Lazy>

    Placeholder

    A placeholder is an image that is shown until the image is in the viewport. data-webpsrc and the optional data-webpplaceholder are only needed if you enable webp detection in the options.

    <Lazy {...options}>
      <img data-placeholder={Placeholder} data-webpplaceholder={PlaceholderWebp} data-src={Image1} data-webpsrc={Image1WebP} alt="butterfly" />
    </Lazy>

    Multiple images in one wrapper

    You can also place multiple images in one wrapper

    <Lazy {...options}>
      <img data-src={Image1} alt="butterfly" />
      <div data-src={Image1} />
      <picture>
        <source media="(min-width:600px)" data-srcset={Image1} />
        <source media="(min-width:500px)" data-srcset={Image2} />
        <img data-src={Image3} alt="butterfly" />
      </picture>
    </Lazy>

    options

    Option Description value default
    waitComplete Wait until the image is fully downloaded before rendering. Doesn't yet support the picture tag. bool true
    webp Ship a webp version if Browser supports it. No need to enable it when working with picture tag as it has its own detection (type="image/webp" - see code examples.). You need to pass the webp version of your picture in data-webpsrc={Image}. bool false
    hideTillRender Hides the image until its rendered as you would otherwise see the alt tag. bool true
    clearAttribute Clear the data-attributes you used to pass the image after its rendered. bool true
    callback Takes a custom callback thats executed after the image is rendered. func null
    root The element that is used as the viewport to check the visiblity of a target. elem browser viewport
    rootMargin Similair to the CSS 'margin' property. It manipulates the elements bounding box. Same syntax as in CSS with either an absolute length or a percentage. px || % 0px 0px 0px 0px
    threshold Indicate at what percentage of the target's visibility the observer's callback should be executed. i.e at an visibility above 50%: 0.5 num (0 -> 1) 0

    Example

    const options = {
      waitComplete: true, 
      webp: true
      hideTillRender: true,
      clearAttributes: true,
      callback: () => console.log("Rendered!"),
      root: document.querySelector('#scrollArea'),
      rootMargin: '50px 0px',
      threshold: 0.75
    };
     
    <Lazy {...options}>
      // image
    </Lazy>

    Polyfill

    For the full support IntersectionObserver polyfill is used.

    Install

    npm i react-lazily-img

    DownloadsWeekly Downloads

    14

    Version

    1.0.71

    License

    ISC

    Unpacked Size

    37.7 kB

    Total Files

    12

    Last publish

    Collaborators

    • marvin_1003