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@seya

Reactで画像をlazyloadしつつpreloadするコンポーネント

FirstViewにはいらんけど、スクロールして登場するまでにはなるべく存在してほしいみたいな画像があったので作ってみました。
正直こんな雑なやり方で合ってるのか分からんのでもっといい方法知ってる人がいたら教えてください頼みます。

import * as React from 'react';

type Props = {
  imgUrl: string;
  alt: string;
};

export default function LazyAndPreloadImage(props: Props) {
  const [loaded, setLoaded] = React.useState(false);

  React.useEffect(() => {
    // preload しておく
    const img = new Image();
    img.src = props.imgUrl;

    // 読み込めたら img タグ描画する
    img.onload = () => {
      setLoaded(true);
    };
  }, []);

  if (loaded) {
    return <img src={props.imgUrl} alt={props.alt} />;
  }

  // 雑に空divにしてるけど思い思いのplaceholder入れてください
  return <div></div>;
}

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seya
最近の趣味はGraphQLとFigmaです。
linc-well
Linc'well(リンクウェル)は2018年創業のヘルスケアスタートアップです。我々は、医療のIT化を通じて、人々と社会の健康に貢献します。

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7
Help us understand the problem. What is going on with this article?