How to send a Blob with other type of data to NodeJS ExpressJS

I searched all the last day an API to send Datas, from Javascript Client Side to the my NodeJS server with express, code below.

app.post('/microphone', express.raw({type: "*/*", limit: '1000000mb' }), function(req, res)
{    
    var buffer = req.body.buffer;

    var nbrVoice = req.body.nbrVoice;
    var codeUser = req.body.codeUser;
    
    var dirUsers = "users/"+codeUser+"/";

        
    fs.appendFileSync(( dirUsers +nbrVoice+ '_microphone.wav'), buffer );

      res.send( "Okay wav file saved );

});

I have a server with expressjs and I want to send a DataView or a Blob with two number

[blob,  codeUser, nbrVoice ]

I tried with xmlhttprequest, a modern version of that call fetch but that not worked and i am blocked with the raw binary data to string to buffer datas on the server.

if someone have an idea I search a code without jquery.