Using [react-native-fs](https://github.com/itinance/react-native-fs) for download file from url, when download progess percent reached 100%, I will call another function. However, `RNFS.downloadFile` not keep track the progress correctly. 

```
_downloadFile = () =>{
  const downloadDest = `${RNFS.ExternalDirectoryPath}/Monstro/${((Math.random() * 1000) | 0)}.jpg`;
  let DownloadFileOptions = {
    fromUrl: "https://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Boothferry_Road%2C_Goole.jpg/220px-Boothferry_Road%2C_Goole.jpg",         
    toFile: downloadDest,           
    begin: this._downloadFileBegin,
    progress: this._downloadFileProgress,
    background:false,
    progressDivider:1
  };

  RNFS.downloadFile(DownloadFileOptions);
}

_downloadFileBegin = () =>{
  console.log("Download Begin");
}

_downloadFileProgress = (data) =>{
  const percentage = ((100 * data.bytesWritten) / data.contentLength) | 0;
  const text = `Progress ${percentage}%`;
  console.log(text);
  if(percentage == 100) //call another function here
}

```

Not every time `console.log` in `_downloadFileProgress` show `Progress 100%`, so it is harder for me to check the progress. Did I miss out some setting, or there is any other ways to keep track the progress