如何判断AudioBufferSourceNode是否已开始播放？

Question

AudioBufferSourceNode摘录：

var myAudioBuffSrcNode = audioContext.createBufferSource();
// Schedules for playback, but doesn't guarantee that
// playback will start right away.
myAudioBuffSrcNode.start();

如何判断节点是否正在播放？所以可以这样做：

if ( isPlaying ) {
  myAudioBufferSrcNode.stop();
}