异步 / 等待 socket.io

Question

此代码将第一个发射发送到客户端，客户端获取消息开始：'作业正在开始...' 这没关系。 之后，代码启动 puppeteer 并制作屏幕截图 example.png。这也可以。 但是第二次发射没有被触发，也没有发送给客户端。 在我得到的服务器的 console.log 中：

• 工作开始
• 捕获完成
• 工作已完成

这也可以。

发生了什么？为什么第二次发射没有触发？

const express = require('express');
const puppeteer = require('puppeteer')
const app = express();
const server = app.listen(3000);

app.set('view engine', 'ejs');
var io = require('socket.io').listen(server);

app.get('/', function (req, res, next) {
  res.render('index');
});

app.get('/scan', function (req, res, next) {
  console.log('job is starting');

  io.sockets.on('connection', function (socket) {
    socket.emit('messageStart', 'Job is starting...');
  });

  (async () => {
    const browser = await puppeteer.launch({headless:false});
    const page = await browser.newPage();
    await page.goto('https://example.com');
    await page.screenshot({ path: 'example.png' });
    await browser.close();
    console.log('CAPTURE FINISHED');
  })().then(()=>{
      console.log('job is finished');

      io.sockets.on('connection', function (socket) {
          socket.emit('messageEnd', 'Job is done!');
        });
    });
  res.render('scan');
});

Answer 1

这里是基于 Md. Abu Taher 代码的完整代码：

const scanner = async () => {
    // emit this message when the scan really starts
    io.sockets.on('connection', function (socket) {
        io.emit('messageDoing', 'Doing the Job ...');
    });
    const browser = await puppeteer.launch({ headless: false });
    const page = await browser.newPage();
    await page.goto('https://example.com');
    await page.screenshot({ path: 'example.png' });
    await browser.close();
    console.log('CAPTURE FINISHED');
};

app.get('/scan', async function (req, res, next) {
    // emit to all clients on start
    console.log('job is starting');
    io.sockets.on('connection', function (socket) {
        io.emit('messageStart', 'Job is starting...');
    });

    // do the actual stuff
    await scanner();

    // emit to all clients on finish
    console.log('job is finished');
    io.sockets.on('connection', function (socket) {
        io.emit('messageEnd', 'Job is done...');
    });
    res.render('scan')
});

Answer 2

你需要监听一次连接并发送到套接字两次。

const scanner = async () => {
  const browser = await puppeteer.launch({headless:false});
  const page = await browser.newPage();
  await page.goto('https://example.com');
  await page.screenshot({ path: 'example.png' });
  await browser.close();
  console.log('CAPTURE FINISHED');
}

app.get('/scan', async function (req, res, next) {
  // emit to all clients on start
  console.log('job is starting');
  io.emit('messageStart', 'Job is starting...');

  // do the actual stuff
  await scanner();

  // emit to all clients on finish
  console.log('job is finished');
  io.emit('messageEnd', 'Job is done!');

  res.render('scan');
});