react的use函数可搭配Suspense与lazy

大猫会长2024-09-04 12:13

use 是一个用于解析 React v18 及以下版本的 promise 状态的 polyfill hook。请注意，它只实现了消费 promise 的能力。

参考资料

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https://www.reactuse.com/zh-Hans/state/use

https://zh-hans.react.dev/reference/react/use#dealing-with-rejected-promises

app.jsx

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import { useState, Suspense, lazy } from 'react';

const Son = lazy(() => delayForDemo(import('./Son.jsx')));

function fn1() {
  return new Promise((res) => {
    setTimeout(res, 1000, { a: { b: 33 } })
  })
}
async function fn2() {
  var res = await new Promise((res) => {
    setTimeout(res, 1000, 'bbbb')
  })
  return res
}
export default function MarkdownEditor() {

  const [dt1, sets] = useState(fn1);
  const [dt2, setb] = useState(fn2);

  return (
    <>
      <Suspense fallback={<div>loading...</div>}>
        <h2>Preview</h2>
        <Son dt1={dt1} dt2={dt2} />
      </Suspense>
    </>
  );
}

// Add a fixed delay so you can see the loading state
function delayForDemo(promise) {
  return new Promise(resolve => {
    setTimeout(resolve, 1200);
  }).then(() => promise);
}

son.jsx

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import { use } from 'react'
export default function MarkdownPreview({ dt1, dt2 }) {
  var d1 = use(dt1)
  var d2 = use(dt2)
  return (
    <>
      <h1>{dt1.a.b}</h1>
      <div>-------</div>
      <h1>{d2}</h1>
    </>
  );
}

只有等待fn1,fn2里的函数 resolve之后,才会显示Son组件

附:延迟promise时间

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延迟特定promise时间
function delay(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

delay(3000).then(() => alert('runs after 3 seconds'));

附:延迟组件加载时间

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//定义
function delayForComp(promise) {
  return new Promise(resolve => {
    setTimeout(resolve, 1200);
  }).then(() => promise);
}

//使用:
import { useState, Suspense, lazy } from 'react';

const Mxxxxx = lazy(() => delayForComp(import('./Mxxxxx.jsx')));



//放在Suspense内部
  return (
    <>
      <Suspense fallback={<div>loading...</div>}>
        <h2>Preview</h2>
        <Mxxxxx dt1={dt1} dt2={dt2} />
      </Suspense>
    </>
  );