最近 Hooks を触って思ったことを綴ります。よく見る useState の increment 例です。 const [count, setCount] = useState(0) const handleClick = () => { setCount(count + 1) } return ( <div className={props.className}> <p>count: {count}</p> <button onClick={handleClick}>+1</button> </div> ) これはアンチパターンで、handleClick は render毎に再定義されます。この再定義を skip するため、useCallback による関数memoizeを行います。 アンチパターン集
![React Hooks、useStateの更新関数引数には関数を - Qiita](https://cdn-ak-scissors.b.st-hatena.com/image/square/0a510a264829153160accc4543fa47c7d894789a/height=288;version=1;width=512/https%3A%2F%2Fqiita-user-contents.imgix.net%2Fhttps%253A%252F%252Fcdn.qiita.com%252Fassets%252Fpublic%252Farticle-ogp-background-412672c5f0600ab9a64263b751f1bc81.png%3Fixlib%3Drb-4.0.0%26w%3D1200%26mark64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTk3MiZoPTM3OCZ0eHQ9UmVhY3QlMjBIb29rcyVFMyU4MCU4MXVzZVN0YXRlJUUzJTgxJUFFJUU2JTlCJUI0JUU2JTk2JUIwJUU5JTk2JUEyJUU2JTk1JUIwJUU1JUJDJTk1JUU2JTk1JUIwJUUzJTgxJUFCJUUzJTgxJUFGJUU5JTk2JUEyJUU2JTk1JUIwJUUzJTgyJTkyJnR4dC1hbGlnbj1sZWZ0JTJDdG9wJnR4dC1jb2xvcj0lMjMyMTIxMjEmdHh0LWZvbnQ9SGlyYWdpbm8lMjBTYW5zJTIwVzYmdHh0LXNpemU9NTYmcz0wMjYxM2FkNjM4MmUxY2FjZDllYmMyY2VkNzYxNzRlNg%26mark-x%3D142%26mark-y%3D57%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZoPTc2Jnc9NzcwJnR4dD0lNDBUYWtlcGVwZSZ0eHQtY29sb3I9JTIzMjEyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTM2JnR4dC1hbGlnbj1sZWZ0JTJDdG9wJnM9NDBiNzM0MDY0NmRiZDcwN2E4MzZiMThiMTBhNjU0OWE%26blend-x%3D142%26blend-y%3D436%26blend-mode%3Dnormal%26txt64%3DaW4g5qCq5byP5Lya56S-44OH44Kj44O844O744Ko44OM44O744Ko44O8%26txt-width%3D770%26txt-clip%3Dend%252Cellipsis%26txt-color%3D%2523212121%26txt-font%3DHiragino%2520Sans%2520W6%26txt-size%3D36%26txt-x%3D156%26txt-y%3D536%26s%3Da204f74762c6d9b67799a32dc6ec9e6b)