compare event based handling of post-request with piping

Project is to support uploading of files and save on SD.
It is tested on ESP32, I don't have hardware to compare with espruino board.
If this is a ESP32 problem only, please move it to ESP32 forum.
Doing the job with piping does not save full upload, some data at the end is missing

function postUpload(req,res){
    var a = url.parse(req.url,true);  //there is a parameter given for location of new file on SD
    var f = E.openFile(a.query.pathname,"w");
    req.pipe(f,{chunkSize:32, end:false,
      complete:function(){
          f.close();
          res.end();
      }
    });
  }

Doing same without piping works fine

function postUpload(req,res){
    var a = url.parse(req.url,true);
    var f = E.openFile(a.query.pathname,"w");
    req.on("data",function(data){f.write(dat­a);});
    req.on("close",function(){
      f.close();
      res.end();
    });
  }