实现代码

/**
* 文件分片
 */
function getFileChunks(file, chunkSize) {
  let chunks = []

  // 默认分片大小 2MB
  let defaultChunkSize = 1024 * 1024 * 2
  chunkSize = chunkSize || defaultChunkSize

  let blobSlice =
    File.prototype.slice ||
    File.prototype.mozSlice ||
    File.prototype.webkitSlice

  let current = 0
  while (current < file.size) {
    let chunk = blobSlice.call(file, current, current + chunkSize)

    chunks.push(chunk)

    current += chunkSize
  }

  return chunks
}

<input
      type="file"
      id="file"
    />

<script>
  document.querySelector('#file').addEventListener('change', function (e) {
    let file = e.target.files[0]
    let chunks = getFileChunks(file, 1024 * 1)
    console.log(chunks)
  })
</script>

文件切片结果