我正在尝试调用recorder.start（）;在我的javascript中，但是控制台错误显示recorder.start（）不是一个函数。我做错了什么？

const recordAudio=async function() {
  const stream = await  navigator.mediaDevices.getUserMedia({ audio: true });
  const mediaRecorder = new MediaRecorder(stream);
  const audioChunks = [];

  mediaRecorder.addEventListener("dataavailable", event => {
    audioChunks.push(event.data);
  });

  let start = function(){ mediaRecorder.start()};
 
};
const handleAction=function() {
const recorder = recordAudio();
const actionButton = document.getElementById('action');
actionButton.disabled = true;
recorder.start();

}