Netlify Functions: issue uploading Blob to S3

Support
3

My current understanding is that Netlify Functions does not support any binary data format, so it just makes everything into a string in JSON.

I created a workaround that I have no idea if it is a good way to solve the problem, nor I’m aware of the trade-offs, but it is working for me. There might be unnecessary steps in it too.

I first transform the Blob (with a mime type of audio/mpeg) generated by the MediaRecorder API into an ArrayBuffer object:

const arrayBuffer = await new Response(audioBlob).arrayBuffer();

This step is necessary because later, inside the Netlify Function, I have to decode the information back into binary data to save on S3, but I am using NodeJS and Node cannot handle a Blob, but it can handle a Buffer.

Then I transform the arrayBuffer into a regular string

const audioBufferStringified = String.fromCharCode(
    ...new Uint8Array(arrayBuffer)
  );

so I can pass it in a JSON to the Netlify Function.

const response = await fetch(
      `/.netlify/functions/upload-audio?user=${user}&filename=${filename}`,
      {
        headers: { Accept: "application/json" },
        method: "POST",
        body: audioBufferStringified
      }
    );

Inside the Netlify Function, I map the string back into an ArrayBuffer object

const audioUint8Array = Uint8Array.from(
      [...audioBufferStringified].map(ch => ch.charCodeAt())
    ).buffer;

and then transform the ArrayBuffer into a Buffer that keeps the mime type audio/mpeg.

const audioBuffer = Buffer.from(audioUint8Array);

This Buffer I can store directly in AWS S3 which can be played later as a valid MP3 file.

const resourceKey = `uploads/${user}/${filename}.mp3`;
const params = {
  Bucket: "bucketname",
  Key: resourceKey,
  Body: audioBuffer,
  ACL: "public-read",
  ContentType: "audio/mpeg",
  ContentDisposition: "inline"
};

const putObjectPromise = await s3.upload(params).promise();

The whole process is:
blob → arraybuffer → string (request to Netlify Function) string → arraybuffer → buffer

I would appreciate comments on any issue with this code that I am missing.