I am trying to read file using JavaScript (readAsBinaryString) and save it to database as bindary data .I am not  going to use Outsystem upload widget .

My goal is to read the file  as Binary data and save to database in small chunk/part .  (For large File) 

problem : The problem is that Binary vairable  that hold file in chunk(part) shows some bytes( like 50000 byte) on client action but that  same varible I send server action  as input it show (o bytes). So some where Binary data lost from client action to server actoin .

I read file  using  var fileInput =document.getElementById($parameters.UploadFileId).fileInput.files[0]  and use readAsBinaryString reader to read binary string  and divide in chunk (part)  then call a clientaciton $actions.SendChunkDataToServer(slice)  and send that chunk variable over client action. 

When I debug I can see in that client action  it show some binary data (50000 bytes) but When I send this input to server action it start showing (o bytes) .

I have attached detail code of JavaScript  in as attachment .Also attaching video of debugging 

JavaScript code like that

var UploadElement =document.getElementById($parameters.UploadFileId);

UploadElement.addEventListener('change', function(){

       var fileInput =document.getElementById($parameters.UploadFileId);

        console.log(fileInput.files[0])

        console.log('Trying to upload the video file: %O', fileInput);

        if ('files' in fileInput) {

            if (fileInput.files.length === 0) {

                alert("Select a file to upload");

            } else {

                UploadVideo(fileInput.files[0]);

            }

        } else {

            console.log('No found "files" property');

        }

    });

 var fileInput =document.getElementById($parameters.UploadFileId);

 UploadVideo(fileInput.files[0]);

function UploadVideo(file) {

    var loaded = 0;

    var chunkSize = 500000;

    var total     = file.size;

    var reader    = new FileReader();

    var slice = file.slice(0, chunkSize);

    reader.readAsBinaryString(slice);      

    // Reading a chunk to invoke the 'onload' event

     console.log('Started uploading file "' + file.name + '"');

    reader.onload = function (e) {

        //Just simulate API

         console.log("Slice Data")

         console.log(slice)

         $actions.SendChunkDataToServer(slice);

          loaded += chunkSize;

          var percentLoaded = Math.min((loaded / total) * 100, 100);

          console.log('Uploaded ' + Math.floor(percentLoaded) + '% of file "' + file.name + '"');

         // $('#uploadVideoProgressBar').width(percentLoaded + "%");

          //Read the next chunk and call 'onload' event again

          if (loaded <= total) {

              slice = file.slice(loaded, loaded + chunkSize);

            reader.readAsBinaryString(slice);

          } else { 

              loaded = total;

            console.log('File "' + file.name + '" uploaded successfully!');

            //$('#uploadVideoProgressBar').hide();

          }

    }

}