节点回调中的异步等待

Question

我有一个使用 3rd 方包的服务。

exports.FOO = (options, cb) => {
  const outputPath = 'bar'
  const storePDF = async (data) => {}
  const sendBack = (outputPath, cb) => {
    fs.readFile(outputPath, encoding, async (err, data) => {
      if (err) {
       return cb(err)
      }
      if (options.source) {
       await store(data)
      }
      cb(null, data);
    })
  }
  ThirdParty.run(err => {
     if (err) {
       return cb(err)
     };
     // read the file and send it back
     sendBack(outputPath, cb)
  })
}

我想升级这个包，但它有一些重大变化，新的用法如下：

await ThirdParty.setup()
await ThirdParty.run()

我真的很想保留回调，因为这个服务在整个应用程序中都是这样使用的。我试图让 FOO async 并在 await ThirdParty.run() 之后调用 sendBack，但我得到了。

node_modules/async/dist/async.js:966

if (fn === null) throw new Error("Callback is already called.");

错误：已调用回调。

exports.FOO = async (options, cb) => {
  const outputPath = 'bar'
  const storePDF = async (data) => {}
  const sendBack = (outputPath, cb) => {
    fs.readFile(outputPath, encoding, async (err, data) => {
      if (err) {
       return cb(err)
      }
      if (options.source) {
       await store(data)
      }
      cb(null, data);
    })
  }
  await ThirdParty.setup()
  await ThirdParty.run()
  sendBack(outputPath, cb)
}

Answer 1

将调用更改为等待。然后像以前一样调用您的回调。如果调用失败，则在catch 块中处理。

exports.FOO = async (options, cb) => {
  //...
  try {
    await ThirdParty.run();
    // read the file and send it back
    sendBack(outputPath, cb)
  } catch (err)
     return cb(err);
  }
}

Answer 2

    exports.FOO = async (options, cb) => {
  const outputPath = 'bar'
  const storePDF = async (data) => {}
  const sendBack = (outputPath, cb) => {
    fs.readFile(outputPath, encoding, async (err, data) => {
      if (err) {
       return cb(err)
      }
      if (options.source) {
       await store(data)
      }
      cb(null, data);
    })
  }
  await ThirdParty.setup()
  await ThirdParty.run()
  sendBack(outputPath, cb) //Why are you calling sendBack here shouldn't be return without calling the function like recursion?
}