use-progressive-image

Hook for progressive image loading, alternative to react-progressive-image.

• Supports <img> and <picture> with <source> elements.
• If image is in browser's cache, loading will be immediatelly false in Chrome, Firefox, and Edge.
• SSR: Returns false on the server, so the server returns image paths instead of placeholders because by the time js is loaded, parsed, and React initialized, most images would have already fully or at least partially loaded. If React is ready and an image is still loading, we have a mismatch and loading is going to be true on the client when that happens. If you want to prevent that, set ssr to true. But this option might not work in development if you're using webpack, probably because webpack dev environment is a little bit magical.
• Written in TypeScript.

Install

$ npm i @ohs/use-progressive-image
$ yarn add @ohs/use-progressive-image

Signature

function useProgressiveImage({
  img?: string | { sizes?: string; src?: string; srcSet?: string; };
  sources?: { sizes?: string; src?: string; srcSet?: string; type?: string; }[];
  ssr?: boolean; // set to true if it's an SSR app
  // returns `loading` and an `Error` event if failed to load
}): [boolean, Event | string | undefined] 

Examples

Simple

import React, { useMemo } from 'react';
import useProgressiveImage from '@ohs/use-progressive-image';

export interface ImgProps {
  lqip?: string;
  src?: string;
}

const Img: React.FC<ImgProps> = ({ lqip, src }) => {
  const [loading] = useProgressiveImage({ img: src });

  return (
    <img src={loading ? lqip : src} />
  );
};

Load avif image with a fallback

import React, { useMemo } from 'react';
import useProgressiveImage from '@ohs/use-progressive-image';

export interface ImgProps {
  lqip?: string;
  src?: string;
  avif?: string;
}

const Img: React.FC<ImgProps> = ({ lqip, src, avif }) => {
  // It's recommended to memoize `sources` array, otherwise it will be deep 
  // compared with previous value on each rerender in `useProgressiveImage`
  const sources = useMemo(() => [{ 
    srcSet: avif, 
    type: 'image/avif' 
  }], [avif]);

  const [loading] = useProgressiveImage({ img: src, sources });

  return (
    <picture>
      {!loading && <source {...sources[0]} />}
      <img src={loading ? lqip : src} />
    </picture>
  );
};