Javascript AbortController.abort(reason)，但是原因在到达 fetch catch 子句之前就丢失了

发布于07月20日

在我的页面上中止抓取主要有两个原因:

用户决定他/她不想再等待AJAX数据，并单击一个按钮；在这种情况下，用户界面显示一条消息"呼叫/任何中断"
用户已移动到页面的另一部分，不再需要获取的数据；在这种情况下，我不希望UI显示任何内容，因为这只会让用户感到困惑

为了区分这两种情况，我计划使用AbortController.abort方法的reason参数，但我的fetch调用中的.catch子句始终接收DOMException('The user aborted a request', ABORT_ERROR).

我试图提供不同的DOMException作为 case 2中中止的原因，但差异消失了.

是否有人找到了如何将信息发送到fetch.catch子句以了解中止的原因？

推荐答案

在下面的示例中，我演示了如何确定fetch请求中止的原因.我提供内联注释进行解释.如果有任何不清楚的地方，请随时发表 comments .

重新运行代码段以查看(可能不同的)随机结果

'use strict';

function delay (ms, value) {
  return new Promise(res => setTimeout(() => res(value), ms));
}

function getRandomInt (min = 0, max = 1) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

// Forward the AbortSignal to fetch:
// https://docs.github.com/en/rest/repos/repos#list-public-repositories
function fetchPublicGHRepos (signal) {
  const headers = new Headers([['accept', 'application/vnd.github+json']]);
  return fetch('https://api.github.com/repositories', {headers, signal});
}

function example () {
  const ac = new AbortController();
  const {signal} = ac;

  const abortWithReason = (reason) => delay(getRandomInt(1, 5))
    .then(() => {
      console.log(`Aborting ${signal.aborted ? 'again ' : ''}(reason: ${reason})`);
      ac.abort(reason);
    });

  // Unless GitHub invests HEAVILY into our internet infrastructure,
  // one of these promises will resolve before the fetch request
  abortWithReason('Reason A');
  abortWithReason('Reason B');

  fetchPublicGHRepos(signal)
    .then(res => console.log(`Fetch succeeded with status: ${res.status}`))
    .catch(ex => {
      // This is how you can determine if the exception was due to abortion
      if (signal.aborted) {
        // This is set by the promise which resolved first
        // and caused the fetch to abort
        const {reason} = signal;
        // Use it to guide your logic...
        console.log(`Fetch aborted with reason: ${reason}`);
      }
      else console.log(`Fetch failed with exception: ${ex}`);
    });

  delay(10).then(() => console.log(`Signal reason: ${signal.reason}`));
}

example();