I am using React Functional Components in my app created with create-react-app, so React.StrictMode is automatically enabled. I don't want to disable it as it is helping me spot potential issues as am developing. Trouble is that it makes the component render twice which creates an error:
Uncaught DOMException: Failed to execute 'createMediaElementSource' on 'AudioContext': HTMLMediaElement already connected previously to a different MediaElementSourceNode as the HTMLMediaElement gets connected in the first render. I am wondering, is there a way to disconnect the HTMLMediaElement from the previous MediaElementSourceNode... maybe set it to null or something, so that it can get a fresh connection?
Here below, is my code that throws the error:

import React, { useEffect, useRef } from "react";

const Canvas = () => {
  const audioRef = useRef(null);
  const filUploadRef = useRef(null);
  const canvasRef = useRef(null);

  let audioSource;
  let analyser;
  let dataArray;

  useEffect(() => {
    const audioElement = audioRef.current;
    const canvas = canvasRef.current;
    const fileUploadField = filUploadRef.current;

    fileUploadField.addEventListener("change", () => {
      const audioContext = new AudioContext();

      const files = fileUploadField.files;
      audioElement.src = URL.createObjectURL(files[0]);
      audioElement.load();
      audioElement.play();

      audioSource = audioContext.createMediaElementSource(audioElement);
      analyser = audioContext.createAnalyser();
      audioSource.connect(analyser);
      analyser.connect(audioContext.destination);
      dataArray = new Uint8Array(analyser.frequencyBinCount);
    });
  }, []);

  const handleTogglePlayPause = () => {
    //TODO: Implement toggle Play/Pause when the button is clicked.
  };

  return (
    <>
      <canvas ref={canvasRef} />
      <audio controls ref={audioRef} />
      <input type="file" id="file-upload" accept="audio/*" ref={filUploadRef} />
      <button onClick={handleTogglePlayPause} type="button">
        {/* ^ This button element is related to handleTogglePlayPause function for a different stage*/}
        Play/Pause
      </button>
    </>
  );
};

export default Canvas;

CodePudding user response：

You can check if audioSource already has a source, and if so you can try to avoid creating a new media element source. Also, you do not need to create a new analyser and connect it.

Add this if check to your code, and it should solve the problem.

// ..
audioElement.play();

if (!audioSource) {
    audioSource = audioContext.createMediaElementSource(audioElement);
    analyser = audioContext.createAnalyser();
    audioSource.connect(analyser);
    analyser.connect(audioContext.destination);
}
//..

Well, react strict mode helps identifying problems, but at the same time it creates new ones. Hence, you might consider closing the strict mode at all.