How to cancel user upload in Formidable (Node.js)?

Question

I have been working on this problem for two days now, and I am stuck. I am using Node.js with Express, and I am trying to implement an upload form. Basically, I want the form to

Answer 1

Here is my solution:

var maxSize = 30 * 1024 * 1024;    //30MB
app.post('/upload', function(req, res) {

    var size = req.headers['content-length'];
    if (size <= maxSize) {
        form.parse(req, function(err, fields, files) {
            console.log("File uploading");
            if (files && files.upload) {
                res.status(200).json({fields: fields, files: files});
                fs.renameSync(files.upload[0].path, uploadDir + files.upload[0].originalFilename);
            }
            else {
              res.send("Not uploading");
            }
        });
    }
    else {
        res.send(413, "File to large");
    }

And in case of wasting client's uploading time before get response, control it in the client javascript.

if (fileElement.files[0].size > maxSize) {
    ....
}