Javascript 为什么我使用更改流得到错误的参数

我正在构建一个应用程序的功能，通过点击列表中的符号（例如：MSFT-Microsoft、AAPL-Apple、GOOG-Google）来绘制图表。符号将由route

router.get（'/app/：symbol'，getWebApi）发送

作为参数，用于从数据库绘制和更新图表数据

数据库在一定的时间间隔内更新，并由

MongoDB-change streams

观察，以将数据推送到前端

on（'change'）

。这是我的问题。当我第一次单击

MSFT

-

req.parms.symbol:MSFT

时，一切都正常工作。第二次单击

AAPL

-

req.parms.symbol:AAPL

first

console.log（）

为我提供了符号的正确参数，但一旦它点击（'change'）它将

console.log（）

从第一次单击开始的符号

MSFT

，并替换为当前参数

AAPL

在第三次点击时，同样的事情也会发生。所以我很困惑为什么我会得到以前单击时调用的参数。如果你有任何想法，我将不胜感激。谢谢大家!

upd:打开更改流时，即使在请求处理程序完成后，它仍保持打开状态。这就解释了为什么当我发出多个API请求时，会在（'change'）事件上得到多个

控制器-stock.js

exports.getWebApi = async (req, res) => {
  try {
    const { symbol } = req.params;

    console.log('on entry req.params.symbol: ', symbol);
    console.log(typeof symbol);

    const apiKeyAlpha = process.env.API_KEY_ALPHAVANTAGE;

    const urlCompact = `https://www.alphavantage.co/query?function=TIME_SERIES_DAILY&symbol=${symbol}&outputsize=compact&apikey=${apiKeyAlpha}`;

    const webApiData = await Db.fetchWebApiStock(urlCompact);
    await Db.creatUpdateStock(symbol, webApiData);

    const db = mongoose.connection;
    const taskCollection = db.collection('stocks');
    const pipeline = [
      {
        $match: {
          'ns.db': 'myapp',
          'ns.coll': 'stocks',
          'fullDocument.symbol': symbol,
        },
      },
    ];

    const options = { fullDocument: 'updateLookup' };
    const changeStream = taskCollection.watch(pipeline, options);

    changeStream.on('change', change => {
      console.log('req.params.symbol in change: ', symbol);

      const { fullDocument } = change;

      const logData = fullDocument.data.map(item => ({
        date: parseFloat(item.date),
        open: parseFloat(item.open),
        high: parseFloat(item.high),
        low: parseFloat(item.low),
        close: parseFloat(item.close),
        volume: parseInt(item.volume),
      }));

      // pusher.trigger(channel, 'AnyEvent', {
      //   chartData: logData,
      //   symbol: fullDocument.symbol,
      // });

    });

    res.send(webApiData);
  } catch (ex) {
    console.log('getWebApi error:', ex);
  }
};

第一次单击时

GET /stock/chart/MSFT 304 22.401 ms - -
GET /JS/chart.js 304 0.282 ms - -
GET /JS/chartWebSearch.js 304 0.286 ms - -
on entry req.parms.symbol:  MSFT
string
GET /stock/app/MSFT 304 896.008 ms - -
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
GET /stock/updatedb 304 908.734 ms - -

第二次单击时

GET /stock/chart/AAPL 304 4.494 ms - -
GET /JS/chart.js 304 0.361 ms - -
GET /JS/chartWebSearch.js 304 0.354 ms - -
on entry req.parms.symbol:  AAPL
string
req.params.symbol in change:  MSFT
GET /stock/app/AAPL 304 558.962 ms - -
req.params.symbol in change:  MSFT
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
GET /stock/updatedb 304 893.851 ms - -

GET /stock/chart/GOOG 304 5.002 ms - -
GET /JS/chart.js 304 0.296 ms - -
GET /JS/chartWebSearch.js 304 0.451 ms - -
on entry req.parms.symbol:  GOOG
string
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  AAPL
GET /stock/app/GOOG 304 741.986 ms - -
req.params.symbol in change:  MSFT
req.params.symbol in change:  GOOG
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  GOOG
req.params.symbol in change:  GOOG
req.params.symbol in change:  GOOG
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  GOOG
req.params.symbol in change:  GOOG
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
GET /stock/updatedb 304 820.259 ms - -

第三次单击时

GET /stock/chart/AAPL 304 4.494 ms - -
GET /JS/chart.js 304 0.361 ms - -
GET /JS/chartWebSearch.js 304 0.354 ms - -
on entry req.parms.symbol:  AAPL
string
req.params.symbol in change:  MSFT
GET /stock/app/AAPL 304 558.962 ms - -
req.params.symbol in change:  MSFT
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
GET /stock/updatedb 304 893.851 ms - -

GET /stock/chart/GOOG 304 5.002 ms - -
GET /JS/chart.js 304 0.296 ms - -
GET /JS/chartWebSearch.js 304 0.451 ms - -
on entry req.parms.symbol:  GOOG
string
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  AAPL
GET /stock/app/GOOG 304 741.986 ms - -
req.params.symbol in change:  MSFT
req.params.symbol in change:  GOOG
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  GOOG
req.params.symbol in change:  GOOG
req.params.symbol in change:  GOOG
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
req.params.symbol in change:  GOOG
req.params.symbol in change:  GOOG
req.params.symbol in change:  AAPL
req.params.symbol in change:  AAPL
req.params.symbol in change:  MSFT
req.params.symbol in change:  MSFT
GET /stock/updatedb 304 820.259 ms - -

请以文本的形式发布文本，而不是文本的图像。您正在不断添加新的
change
处理程序。@DaveNewton不是当我更改网页时，
change
处理程序被杀死的人？@DaveNewton我很困惑。它是如何工作的呢？这里没有离开寻呼机的导航——如果页面重新加载，是的，所有当前的js代码都会消失。如果您毫不犹豫地添加了一个处理程序，在每次执行getWebApi时都有一个闭包，这将准确地解释您看到的内容。