Send blob data to node using fetch, multer, express

Question

Trying to send a blob object to my node server. On the client side I\'m recording some audio using MediaRecorder and then I want to send the file to my server for processing.

Answer 1

I was just able to run a minimum configuration of your above example and it worked fine for me.

Server:

var express = require('express');
var multer  = require('multer');
var app = express();

app.use(express.static('public')); // for serving the HTML file

var upload = multer({ dest: __dirname + '/public/uploads/' });
var type = upload.single('upl');

app.post('/api/test', type, function (req, res) {
   console.log(req.body);
   console.log(req.file);
   // do stuff with file
});

app.listen(3000);

HTML file in public:

<script>
var myBlob = new Blob(["This is my blob content"], {type : "text/plain"});
console.log(myBlob);

// here unnecessary - just for testing if it can be read from local storage
localStorage.myfile = myBlob;

var fd = new FormData();
fd.append('upl', localStorage.myfile, 'blobby.txt');

fetch('/api/test',
{
    method: 'post',
    body: fd
}); 
</script>

The console.log(myBlob); on the frontend is printing Blob {size: 23, type: "text/plain"}. The backend is printing:

{}
{ fieldname: 'upl',
  originalname: 'blobby.txt',
  encoding: '7bit',
  mimetype: 'text/plain',
  destination: '/var/www/test/public/uploads/',
  filename: 'dc56f94d7ae90853021ab7d2931ad636',
  path: '/var/www/test/public/uploads/dc56f94d7ae90853021ab7d2931ad636',
  size: 23 }

Maybe also try it with a hard-coded Blob like in this example for debugging purposes.