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React component for progressive image loading
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README.md

React Progressive Image

react-progressive-image React component for progressive image loading

Install

$ yarn add react-progressive-image

The UMD build is also available on unpkg:

<script src="https://unpkg.com/react-progressive-image@0.1.0/umd/react-progressive-image.min.js"></script>

If you use the UMD build you can find the library on window.ReactProgressiveImage.

Examples

Simple

<ProgressiveImage src="large-image.jpg" placeholder="tiny-image.jpg">
  {src => <img src={src} alt="an image" />}
</ProgressiveImage>

With Delay

<ProgressiveImage
  delay={3000}
  src="large-image.jpg"
  placeholder="tiny-image.jpg"
>
  {src => <img src={src} alt="an image" />}
</ProgressiveImage>

With loading argment

<ProgressiveImage src="large-image.jpg" placeholder="tiny-image.jpg">
  {(src, loading) => (
    <img style={{ opacity: loading ? 0.5 : 1 }} src={src} alt="an image" />
  )}
</ProgressiveImage>

With srcSet

<ProgressiveImage
  src="medium.jpg"
  srcSetData={{
    srcSet: 'small.jpg 320w, medium.jpg 700w, large.jpg 2000w',
    sizes: '(max-width: 2000px) 100vw, 2000px'
  }}
  placeholder="tiny-image.jpg"
>
  {(src, _loading, srcSetData) => (
    <img
      src={src}
      srcSet={srcSetData.srcSet}
      sizes={srcSetData.sizes}
      alt="an image"
    />
  )}
</ProgressiveImage>

Component As Placeholder

If you want to use a component, such as a loading spinner, as a placeholder, you can make use of the loading argument in the render callback. It will be true while the main image is loading and false once it has fully loaded. Keep in mind that the placeholder props is required, so you will need to explicitly declare an empty string as it's value if you plan on using a component in the render callback.

const dominantImageColor = '#86356B';
const placeholder = (
  <div
    style={{ backgroundColor: dominantImageColor, height: 300, width: 500 }}
  />
);

<ProgressiveImage src="large-image.jpg" placeholder="">
  {(src, loading) => {
    return loading ? placeholder : <img src={src} alt="an image" />;
  }}
</ProgressiveImage>;

Progressive Enhancement and No JavaScript

Since this component relies on JavaScript to replace the placeholder src with the full image src, you should use a fallback image if your application supports environments that do not have JavaScript enabled or is progressively enhanced.

You can do this by adding the fallback image inside of a <noscript> tag in the render callback you provide as the ProgressiveImage component's child.

<ProgressiveImage src="large-image.jpg" placeholder="tiny-image.jpg">
  {src => {
    return (
      <div>
        <img className="progressive-image" src={src} />
        <noscript>
          <img className="progressive-image no-script" src="large-image.jpg" />
        </noscript>
      </div>
    );
  }}
</ProgressiveImage>

Props

Name Type Required Description
children function true returns src, loading, and srcSetData
delay number false time in milliseconds before src image is loaded
onError function false returns error event
placeholder string true the src of the placeholder image
src string true the src of the main image
srcSetData {srcSet: "string", sizes: "string" } false srcset and sizes to be applied to the image
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