Validate Download Size

Hi all,
I’m trying to solve a simple problem but it seems in js it’s not that simple as expected :frowning:
I have an app (Android, iOS) which is playing some videos which are downloaded from a server and locally stored.
For the download I use the FileTransferObject from ‘@ionic-native/file-transfer’ which works like expected.

      await, this.filepath + dest)
      .then((entry) => {
        console.log('loaded: ' , entry );

          entry.file(function (file) {
            var reader = new FileReader();
            reader.onloadend = function() {
              console.log("Successful file read: " + this.result);
              let tmp: ArrayBuffer = this.result;              
              console.log('tmp.byteLength: ', tmp.byteLength)

At the end of the download I want to validate the local stored filesize against my stored file info which also has the size of the original file.
FileReader has not such a property and the byteLength is not the filesize.
Any hints how to get the size of a local stored file?