小编New*_*eX2的帖子

我已经尝试过阅读指南和教程来异步/等待,但我似乎无法在任何地方找到这个.

这是有问题的代码:

    var func1 = new Promise((resolve, reject) => {
      console.log("Func1");
      setTimeout(() => {
        resolve(10);
      }, 100);
    });
    
    var func2 = new Promise((resolve, reject) => {
      console.log("Func2");
      setTimeout(() => {
        resolve(20);
      }, 5000);
    })
    
    let run = async() => {
      let var1 = await func1;
      let var2 = await func2;
      console.log(var1);
      console.log(var2);
    }

    run();

我们看到"Func1"和"Func2"立即打印,一个接一个.5秒后,在func2中指定超时,我们打印"10"和"20".到现在为止还挺好.

但是,如果我将最后一段代码更改为:

let run = async() => {
  let var1 = await func1;
  console.log(var1);
  let var2 = await func2;
  console.log(var2);
}

然后我看到"Func1"立即打印,但"Func2"也是如此,即使console.log(var1)它在它之前.100ms后"10",然后5秒后"20".

来自MDN:

await表达式导致异步函数执行暂停,直到Promise被完成或拒绝,并在执行后继续执行async函数. …

Create-react-app 附带一个 registerServiceWorker.js 文件，其中包含注册服务工作者的代码。我只是有点困惑它是如何工作的。有问题的代码是：

function registerValidSW(swUrl) {
  navigator.serviceWorker
    .register(swUrl)
        .then(registration => {
      registration.onupdatefound = () => {
        const installingWorker = registration.installing;
        installingWorker.onstatechange = () => {
          if (installingWorker.state === 'installed') {
            if (navigator.serviceWorker.controller) {
              // At this point, the old content will have been purged and
              // the fresh content will have been added to the cache.
              // It's the perfect time to display a "New content is
              // available; please refresh." message in your web app.
              console.log('New content is …