Send blob data to node using fetch, multer, express

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 filevar 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 storagelocalStorage.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.