file upload from axios to busboy never finishes

Question

This is my simple code for file upload. I use nodejs with busboy on server and axios with react on client. I select file, submit the form and I see only /upload being handled on the server side:

app.post('/upload', function (req, res) {
    console.log("upload"); // we do get here
    if (req.busboy) {
         // and here
        req.busboy.on("file", function (fieldName, fileStream, fileName, encoding, mimeType) {
            console.log("on file"); // but never get here
        });
        return req.pipe(req.busboy);
    }
});

But on("file") callback is never called. This is my client code: client code:

<input type="file" onChange={this.getFile} />

getFile(e){
    e.preventDefault();
    let reader = new FileReader();
    let file = e.target.files[0];
    reader.onloadend = (theFile) => {
        const data = new FormData();
        data.append('file', file);
        axios.post("/upload",file);
    };
    reader.readAsDataURL(file);
}

What can be the problem?

UPDATE: req.body is undefined. I've added these lines:

var bodyParser = require('body-parser');
app.use(bodyParser.urlencoded({extended: false, limit: '50mb'}));

req.body is not null and contains file buffer, but on('file') is not launched yet.

Answer 1

The bug was here:

reader.onloadend = (theFile) => {
    const data = new FormData();
    data.append('file', file); 
    axios.post('/upload', data); // <-- I had wrong second argument here!
};