My code for uploading,**client side**:
              var uploadInstance = Images.insert({
                file: file,
                streams: 'dynamic',
                chunkSize: 'dynamic'
              }, false);
              uploadInstance.on('start', function() {
                      this.currentUploadvar = 1;
                      console.log(this.currentUploadvar);
                     });
              uploadInstance.on('end', function(error, fileObj) {
                  if (error) {
                      alert('Error during upload: ' + error.reason);
                      } else {
                      alert('File "' + fileObj.name + '" successfully uploaded');
                              }
                      // console.log('Upload Ended');
                      //  this.currentUpload.set(false);
                      this.currentUploadvar = 0;
                      });

              uploadInstance.start();