Preact setState钩子不能在setInterval中工作

Question

CodeSandbox 试图在useState的setInterval内的preact/hook。这不起作用，看似永远迭代它正在执行以前的callstacks（？）。有人可以帮助我理解并帮助我解决这个问题吗？

import {h} from 'preact';
import {useState} from 'preact/hooks'
const interests = [
  {name: 'the future',},
  {name: 'architecture',},
  {name: 'my work',},
  {name: 'your work',},
  {name: 'collaboration',},
  {name: 'dank memes',},
  {name: 'OOP vs. Functional',},
  {name: 'design',},
  {name: 'guitar',},
  {name: 'inspirational people',},
  {name: 'love',},
  {name: 'travel',},
  {name: 'singularity',},
  {name: 'creativity',},
  {name: 'mixed, virtual, augmented reality',},
  {name: 'art',},
  {name: 'imagination',},
  {name: 'problem solving',},
  {name: 'space',},
  {name: 'cooking',},
  {name: 'FOMO',},
  {name: 'ontological design',},
  {name: 'flow state',},
  {name: 'foreign languages',},
  {name: 'streaming on the internet',},
  {name: 'video games',},
  {name: 'coffee',},
  {name: 'crypto currency',},
  {name: 'javascript fatigue',},
  {name: 'framework wars',},
  {name: 'blockchain',},
  {name: 'smart contracts',},
  {name: 'just emailing me'},
  {name: 'ethereum'},
  {name: 'university'},
  {name: 'engineering software'},
];


const RunningHeader = () => {
  const [count, setCount] = useState(0);
  setInterval(() => {setCount(c => c + 1)}, 1000);
  return (
    <header>
      <p>{interests[count].name}</p>
    </header>
)}

export {RunningHeader};

Answer 1

您需要使用setTimeout。 setInterval永远不会被取消，因此每个渲染都会添加一个新的1s重复计时器。这是你的沙盒以两种不同的方式固定（setTimeout或使用useEffect在mount上安装重复计时器）：

https://codesandbox.io/s/vy0ww725j0

Answer 2

useEffect没有依赖关系[]将作为componentDidMount来挂载我们的间隔，我们可以返回一个函数来调用unmount，我们应该在unmount上清除我们的internval以避免内存泄漏。

useEffect(() => {
  const id = setInterval(() => {
    setCount(c => c + 1);
  }, 1000);
  return () => clearInterval(id);
}, []);