回答編集履歴
5
ついき
test
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@@ -215,3 +215,35 @@
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[=> Demo](https://codesandbox.io/s/641l14jmlr)
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# 追記
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```
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import throttle from 'lodash.throttle';
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//(中略)
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handleScroll = throttle((event) => {
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this.setState({
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scrollTop: this.node.scrollTop
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})
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}, 100)
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```
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scrollする度に処理を走らせてしまうのはパフォーマンス的にしんどいので、100ミリ秒毎に処理を走らせるように`lodash`の`throttle`で`scroll`イベントを間引きました。
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4
throttleを追加
test
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@@ -20,6 +20,8 @@
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import ReactDOM from "react-dom";
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import throttle from 'lodash.throttle';
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class App extends Component {
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handleScroll = (event) => {
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handleScroll = throttle((event) => {
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this.setState({
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})
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}
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}, 100)
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import ReactDOM from "react-dom";
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import throttle from 'lodash.throttle';
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class App extends Component {
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handleScroll = (event) => {
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handleScroll = throttle((event) => {
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this.setState({
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scrollTop: this.node.
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scrollTop: this.node.scrollTop
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})
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}
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}, 100)
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ReactDOM.render(<App />, rootElement);
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```
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3
a
test
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# 回答
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雑な書き捨てコードですが、こんな感じで出来ます。
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# キャプチャー画像(animation Gif)
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a
test
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# コード
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# コード(React 16.3以前)
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```ここに言語を入力
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[=> Demo](https://codesandbox.io/s/40wxzzv1y7)
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# コード(React 16.3以降)
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```
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import React, { Component } from "react";
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import ReactDOM from "react-dom";
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class App extends Component {
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constructor(props) {
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super(props);
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this.node = React.createRef();
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}
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state = {
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scrollTop: 0
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}
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handleScroll = (event) => {
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this.setState({
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scrollTop: this.node.current.scrollTop
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})
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}
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render() {
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return (
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<div>
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<div
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style={{
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overflowY: 'scroll',
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height: '50px',
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backgroundColor: '#ccc'
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}}
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onScroll={this.handleScroll}
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ref={this.node}
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>
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<p style={{ fontSize: '50px' }}>Hello World</p>
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</div>
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<p>Scroll Top: {this.state.scrollTop}</p>
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</div>
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);
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}
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}
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const rootElement = document.getElementById("root");
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ReactDOM.render(<App />, rootElement);
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```
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[=> Demo](https://codesandbox.io/s/641l14jmlr)
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1
https://teratail.storage.googleapis.com/uploads/contributed_images/b99554161f0ee4a45f262740d256018c.
test
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# キャプチャー画像(animation Gif)
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[=> animation Gif](https://teratail.storage.googleapis.com/uploads/contributed_images/b99554161f0ee4a45f262740d256018c.gif)
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# コード
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```ここに言語を入力
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[=> Demo](https://codesandbox.io/s/40wxzzv1y7)
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