title: what is busboy.on('field', function() } is can any one solve it
body: <p>my TL asked me to go through the below code while going through the code i stuck at at what is busboy.on('field', function() } is can any one solve it and why we are using reqpipe method at the end ?</p>
  <pre><code>   app.post('/fileupload', function (req, res) {
      var busboy =  Busboy({ headers: req.headers });
      //  const tmpdir = os.tmpdir();
      const uploads = {};
      const fields = {};
  
      busboy.on('file', async function(fieldname, file, filename, encoding, mimetype) {
        //  console.log(`Processed file ${file}`);
        uploads[fieldname] = filename;
        // console.log(uploads.file.filename);
      var saveTo = path.join(__dirname, uploads.file.filename);
      const writeStream = fs.createWriteStream(saveTo);
      file.pipe(writeStream);
     
      });
  
      busboy.on('field', function(fieldname, val, fieldnameTruncated, valTruncated, encoding, 
      mimetype) {
    
      fields[fieldname] = val;
      console.log(fields)
      });
  
  
      busboy.on('finish', function() {
      res.writeHead(200, { 'Connection': 'close' });
      res.end(&quot;That's all folks!&quot;);
      
      });
    
      return req.pipe(busboy);    
      });
  </code></pre>