使用spark-md5获取文件md5值

网上搜到的文章都乱七八糟的，参照官方例子稍微改了改

/**
 * 分片获取md5值
 * @param {*} file 文件对象
 * @param {*} chunkSize 分片大小
 * @param {*} progressCallback 进度修改回调
 * @returns 
 */
function md5WithChunk(file, chunkSize, progressCallback = console.log) {
  return new Promise((resolve, reject) => {
    const blobSlice =
      File.prototype.slice ||
      File.prototype.mozSlice ||
      File.prototype.webkitSlice
    let chunks = Math.ceil(file.size / chunkSize)
    let currentChunk = 0
    let spark = new SparkMD5.ArrayBuffer()
    let fileReader = new FileReader()
    fileReader.onerror = reject
    fileReader.onload = (e) => {
      processCallback(currentChunk / chunks)
      spark.append(e.target.result)
      currentChunk++
      if (currentChunk < chunks) {
        loadNext()
      } else {
        resolve(spark.end())
      }
    }
    function loadNext() {
      let start = currentChunk * chunkSize
      let end = start + chunkSize >= file.size ? file.size : start + chunkSize
      fileReader.readAsArrayBuffer(blobSlice.call(file, start, end))
    }
    loadNext()
  })
}

使用

<input id="file" type="file" onchange="showMd5(this.files[0])">
<script>
async function showMd5(file) {
  let md5  = await md5WithChunk(file,2*1024**2) //2MB
  console.log(md5);
}
<script>

效果（控制台）

0
0.006896551724137931
0.013793103448275862
0.020689655172413793
....
0.9862068965517241
0.993103448275862

9f120ab831064012ff641ca83e918057