Web MIDI API -如何检查send()方法是否已完成？

// 请求访问MIDI设备
navigator.requestMIDIAccess()
  .then(function(midiAccess) {
    // 获取已连接的MIDI设备
    var devices = midiAccess.inputs.values();
    for (var device = devices.next(); device && !device.done; device = devices.next()) {
      // 监听MIDI消息
      device.value.onmidimessage = function(event) {
        // 处理MIDI消息
        console.log('Received MIDI message', event.data);
      };
    }

    // 发送MIDI消息
    var output = midiAccess.outputs.values().next().value;
    var message = [0x90, 60, 100]; // 示例：发送一个音符
    var result = output.send(message);

    if (result === false) {
      console.log('Failed to send MIDI message');
    }
  })
  .catch(function(error) {
    console.log('Failed to access MIDI devices', error);
  });