js：spark-md5分片计算文件的md5值

<script src="https://cdn.bootcdn.net/ajax/libs/spark-md5/3.0.2/spark-md5.min.js"></script>

npm install --save spark-md5

var hexHash = SparkMD5.hash('Hi there')
console.log(hexHash)
// d9385462d3deff78c352ebb3f941ce12

var spark = new SparkMD5()
spark.append('Hi')
spark.append(' ')
spark.append('there')
var hexHash = spark.end()
console.log(hexHash)
// d9385462d3deff78c352ebb3f941ce12

<script src="https://cdn.bootcdn.net/ajax/libs/spark-md5/3.0.2/spark-md5.min.js"></script>
<input
  type="file"
  id="file"
/>
<script>
  /**
   * 计算文件md5值
   */
  function getFileMd5(file) {
    return new Promise((resolve, reject) => {
      let fileReader = new FileReader()
      fileReader.onload = function (event) {
        let fileMd5 = SparkMD5.ArrayBuffer.hash(event.target.result)
        resolve(fileMd5)
      }
      fileReader.readAsArrayBuffer(file)
    })
  }
  document.getElementById('file').onchange = function (event) {
    let file = event.target.files[0]
    getFileMd5(file).then((md5) => {
      console.log(md5)
      // e311a516191b1643e3f63cb05163d11a
    })
  }
</script>

<script src="https://cdn.bootcdn.net/ajax/libs/spark-md5/3.0.2/spark-md5.min.js"></script>
<input
  type="file"
  id="file"
/>
<script>
  /**
   * 分片读取文件，计算最终md5值
   */
  function getFileMd5BySlice(file, chunkSize) {
    // 默认分片大小 2MB
    let defaultChunkSize = 1024 * 1024 * 2
    return new Promise((resolve, reject) => {
      chunkSize = chunkSize || defaultChunkSize
      let blobSlice =
          File.prototype.slice ||
          File.prototype.mozSlice ||
          File.prototype.webkitSlice,
        // 总分片数
        chunks = Math.ceil(file.size / chunkSize),
        currentChunk = 0,
        spark = new SparkMD5.ArrayBuffer(),
        fileReader = new FileReader()
      fileReader.onload = function (e) {
        console.log('read chunk nr', currentChunk + 1, 'of', chunks)
        spark.append(e.target.result) // Append array buffer
        currentChunk++
        if (currentChunk < chunks) {
          loadNext()
        } else {
          resolve(spark.end())
        }
      }
      fileReader.onerror = function (error) {
        reject(error)
      }
      function loadNext() {
        // 切片起始位置
        let start = currentChunk * chunkSize
        // 切片终止位置
        let end = start + chunkSize
        if (end >= file.size) {
          end = file.size
        }
        fileReader.readAsArrayBuffer(blobSlice.call(file, start, end))
      }
      loadNext()
    })
  }
  document.getElementById('file').addEventListener('change', function (e) {
    let startTime = new Date().getTime()
    let file = e.target.files[0]
    getFileMd5BySlice(file).then((res) => {
      console.log(res)
      // 52fde8264e2640cd5b95fdb123de0eba
      console.log(new Date().getTime() - startTime)
      // 4611 2M
      // 4167 10M
      // 4333 20M
      // 4070 50M
      // 4160 100M
    })
  })
</script>