在另一个[重复]中运行一个异步函数

Question

我第一次尝试在 NodeJS 中做一些异步操作时有点卡住了。我阅读了一些关于 Promises 和 async/await 的内容，但仍然对在一个异步函数位于另一个异步函数内部的情况下最好的做法感到困惑。

function startTheater(sourceAudioFile) {
  decodeSoundFile(sourceAudioFile).then((result) => {
    setLight(); //this has to run only run after decodeSoundFile is complete
  });
}

function decodeSoundFile(soundfile) {
  return new Promise(function(resolve, reject) {
    fs.readFile(soundfile, function(err, buf) {
      if (err) throw err
      context.decodeAudioData(buf, function(audioBuffer) {
      playSound();
        findPeaks(pcmdata, samplerate); <<<<<< this function itself has has to finish before decodeSoundFile returns <<<<<<
     if (lightPlant.length != 0) {
        resolve("light plan populated");
      } else {
        reject(new Error("broke promise. unable to populate"));
      }
      }, function(err) {
        throw err
      })
    })
  });
}

以下函数需要一段时间才能完成，但上面的decodeSoundFile 在完成之前返回。当decodeSoundFile 本身就是一个承诺时，我该如何防止这种情况发生？

function findPeaks(pcmdata, samplerate) {
  var interval = 0.5 * 1000;
  var step = samplerate * (interval / 1000);

  //loop through sound in time with sample rate
  var samplesound = setInterval(function() {
    if (index >= pcmdata.length) {
      clearInterval(samplesound);
      console.log("finished sampling sound"); <<this is where decodeSoundFile is good to return after findPeaks execution. 
    }

    for (var i = index; i < index + step; i++) {
      max = pcmdata[i] > max ? pcmdata[i].toFixed(1) : max;
    }
    prevmax = max;
    max = 0;
    index += step;
  }, interval, pcmdata);
}

我如何以正确的方式执行此链接？

Answer 1

import { readFile } from 'fs/promises';

function startTheater(sourceAudioFile) {
    decodeSoundFile(sourceAudioFile).then((result) => {
        setLight(); //this has to run only run after decodeSoundFile is complete
    });
}

function decodeSoundFile(soundfile) {
    return fs.readFile(soundfile)
    .then(buf => new Promise((resolve, reject) => context.decodeAudioData(buf, resolve, reject)))
    .then(audioBuffer => {
        playSound();
        return findPeaks(pcmdata, samplerate);
    })
    .then(() => {
        if (lightPlant.length != 0) {
            return "light plan populated";
        } else {
            return Promise.reject(new Error("broke promise. unable to populate"));
        }        
    });
}

function findPeaks(pcmdata, samplerate) {
    return new Promise(function (resolve, reject) {
        var interval = 0.5 * 1000;
        var step = samplerate * (interval / 1000);

        //loop through sound in time with sample rate
        var samplesound = setInterval(function () {
            if (index >= pcmdata.length) {
                clearInterval(samplesound);
                console.log("finished sampling sound");
                resolve();
            }
            for (var i = index; i < index + step; i++) {
                max = pcmdata[i] > max ? pcmdata[i].toFixed(1) : max;
            }
            prevmax = max;
            max = 0;
            index += step;
        }, interval, pcmdata);
    });
}

根据要求（和 startTheater）在 decodeSoundFile 中使用 async/await

async function startTheater(sourceAudioFile) {
    const result = await decodeSoundFile(sourceAudioFile);
    setLight();
}

async function decodeSoundFile(soundfile) {
    const buf = await fs.readFile(soundfile);
    const audioBuffer = await new Promise((resolve, reject) => context.decodeAudioData(buf, resolve, reject));
    await findPeaks(pcmdata, samplerate);
    if (lightPlant.length != 0) {
        return "light plan populated";
    } else {
        return throw new Error("broke promise. unable to populate");
    }        
}