When playing audio in JavaScript, the error "play() failed because the user didn't interact with the document first." occurs.

This error occurs because many mobile browsers prevent JavaScript from initiating playback of media elements unless it's in response to user interaction. This is to prevent users from being bombarded with unwanted audio.

There are a few ways to work around this error. One way is to use a button or other element that the user can click to start playback. Another way is to use the play() method with a promise. This will allow you to check the status of the playback request and handle any errors that occur.

Here is an example of how to use the play() method with a promise:

const audio = document.querySelector('audio');

async function playAudio() {
  try {
    await audio.play();
  } catch (error) {
    console.log(error);
  }
}

playAudio();

This code will first try to play the audio. If an error occurs, the error will be logged to the console.

Here is an example of how to use a button to start playback:

const audio = document.querySelector('audio');
const playButton = document.querySelector('button');

playButton.addEventListener('click', () => {
  audio.play();
});

This code will create a button that, when clicked, will start playing the audio.

I hope this helps! Let me know if you have any other questions.