Question

我有以下功能

function calculateMFCC (wavFile, clipID) {
  var audioData = loadAudioData(wavFile);
  clipId = clipID;
  passToWavReader(audioData);
}

函数loadAudioData（wavFile）应该使用Ajax加载wav文件并将结果作为arraybuffer返回。这就是它的样子：

function loadAudioData(wavFile) {
  var request = new XMLHttpRequest();
    request.open('GET', wavFile, false);
    //request.responseType = 'arraybuffer';
    request.onload = function() {
        var audioData = stringToArrayBuffer(request.response);
      //passToWavReader(audioData);
      return audioData;
    }
    request.send();
}

当我调试脚本时，我看到在loadAudioData（wavFile）函数中，变量audioData获取它应该获取的值，但是当它返回函数calculateMFCC（wavFile，clipID）时，值audioData是未定义的，所以当它调用passToWavReader（audioData）脚本中断。因此，来自calculateMFCC的audioData变量以某种方式没有从loadAudioData获取值。

Answer 1

问题是XMLHttpRequest不会立即响应。您需要添加回调。尝试：

function calculateMFCC (wavFile, clipID) {
  loadAudioData(wavFile, function(audioData) {
    clipId = clipID;
    passToWavReader(audioData);
  });
}

function loadAudioData(wavFile, callback) {
  var request = new XMLHttpRequest();
  request.open('GET', wavFile, false);
  //request.responseType = 'arraybuffer';
  request.onload = function() {
    var audioData = stringToArrayBuffer(request.response);
    //passToWavReader(audioData);
    callback(audioData);
  }
  request.send();
}

函数在javascript中返回null

1 个答案: