Splitting a File into Chunks with Javascript

Question

I'm trying to take a single file object and split it into chunks by a specified chunk size. In my example, trying to split a single file into 1MB chunks. So I figure out how many chunks it would take, then I'm trying to slice the file starting from the 'offset' (current chunk I'm on * chunk size), and slicing off a chunk size. My first slice comes out properly at 1MB but my subsequent slices turn out to 0, any ideas why? Have a working codepen here:

http://codepen.io/ngalluzzo/pen/VvpYKz?editors=001[1]

var file = $('#uploadFile')[0].files[0];
  var chunkSize = 1024 * 1024;
  var fileSize = file.size;
  var chunks = Math.ceil(file.size/chunkSize,chunkSize);
  var chunk = 0;

  console.log('file size..',fileSize);
  console.log('chunks...',chunks);

  while (chunk <= chunks) {
      var offset = chunk*chunkSize;
      console.log('current chunk..', chunk);
      console.log('offset...', chunk*chunkSize);
      console.log('file blob from offset...', offset)
      console.log(file.slice(offset,chunkSize));
      chunk++;
  }

Answer 1

Was slicing off the wrong ends:

console.log(file.slice(offset,chunkSize));

should have been

console.log(file.slice(offset,offset+chunkSize));

Answer 2

Use The function below to split a big file into multiple chunks. I have used it with react, it's works.

  createChunks = (file,cSize/* cSize should be byte 1024*1 = 1KB */) => {
   let startPointer = 0;
   let endPointer = file.size;
   let chunks = [];
   while(startPointer<endPointer){
    let newStartPointer = startPointer+cSize;
    chunks.push(file.slice(startPointer,newStartPointer));
    startPointer = newStartPointer;
   }
   return chunks;
  }