是否可以继续暂停异步功能？ （2） [英] Is it possible continue a paused async function? (2)

问题描述

我在之前的代码中做了一些更改，运行了更多测试，我又遇到了同样的问题（是否可以继续停止异步功能？）。所以这个问题是相关的。

I've made some changes in the previous code, running more tests, and I've run into the same problem again (Is it possible continue a stopped async function?). So this question is related.

此外，之前的解决方案不起作用。

Furthermore, the previous solution does not work.

var stop = false;
var pause = false;
var elParrafo = document.getElementById('miParrafo');

function sendPause() {
  pause = true;
}

function sendContinue() {
  pause = false;
}

function sendStop() {
  stop = true;
}

function longWork(ms, char) {
  return new Promise(function(resolve, reject) {
    elParrafo.innerHTML += char;
    setTimeout(resolve, ms);
  });
}

async function doIt() {
  for (var i = 0; i < 666; i++) {
    if (!stop) {
      if (!pause) {
        await longWork(50," > ");
      }
    } else {
      break;
    }
  }
}

doIt();

<form class="" action="index.html" method="post">
  <input type="button" value="Pause" onclick="sendPause()">
  <input type="button" value="Continue" onclick="sendContinue()">
  <input type="button" value="Stop" onclick="sendStop()">
</form>
<p id="miParrafo"></p>

推荐答案

将flags设置为true时会出现问题。在取消设置标志时，异步代码会耗尽循环的其余部分。你可以用一些承诺绕过它。

The issue occurs when you set the flags to true. The async code exhausts the rest of the loop doing nothing by the time you unset the flags. You can get around it with some promises instead.

let stop = false;
let isPaused = false;
let resolvePause = () => {};
let pauseProm = Promise.resolve();
const elParrafo = document.getElementById('miParrafo');

function sendPause() {
  if(isPaused) return;

  isPaused = true;
  pauseProm = new Promise(resolve => resolvePause = resolve);
}

function sendContinue() {
  isPaused = false;
  resolvePause();
}

function sendStop() {
  stop = true;
}

function longWork(ms, char) {
  return new Promise(function(resolve, reject) {
    elParrafo.innerHTML += char;
    setTimeout(resolve, ms);
  });
}

async function doIt() {
  for (let i = 0; i < 666; i++) {
    if (stop) break;

    await pauseProm;
    await longWork(50," > ");
  }
}

doIt();

<form class="" action="index.html" method="post">
  <input type="button" value="Pause" onclick="sendPause()">
  <input type="button" value="Continue" onclick="sendContinue()">
  <input type="button" value="Stop" onclick="sendStop()">
</form>
<p id="miParrafo"></p>

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