React.js ライブラリ「reactjs-visibility」を使って表示・非表示を検出する

yarn global add create-react-app
npx create-react-app react-app

## 作成したプロジェクトに移動
cd react-app
 
## インストール
yarn add reactjs-visibility

import React from 'react'
import { VisibilityObserver } from 'reactjs-visibility'

const Sample = () => {
    const handleChangeVisibility = (visible) => {
        if (visible) {
            alert("I am now visible");
        }
    };

    const options = {
        rootMargin: "300px",
    };

    return (
        <div>
            <h1 style={{ fontSize: 20 }}>
                Lorem ipsum dolor sit, amet consectetur adipisicing elit. Magni nam
                exercitationem sit alias perferendis, odit ex optio iure assumenda!
                Voluptatum, nulla. Assumenda iusto nesciunt adipisci totam repellat id
                excepturi minima.
            </h1>

            <VisibilityObserver
                onChangeVisibility={handleChangeVisibility}
                options={options}
            >
                Loadmore...
            </VisibilityObserver>
        </div>
    );
};

export default Sample;

import React from 'react';
import Sample from './sample';
import './App.css';

function App() {
  const style = {
    width: "30%",
    margin: "0 auto",
    marginTop: 150,
  };
  return (
    <div className="App">
      <div style={style}>
        <Sample />
      </div>
    </div>
  );
}

export default App;

yarn start