Splitting a File into Chunks with Javascript

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;
  }

Was slicing off the wrong ends:

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

should have been

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