js计算md5

import SparkMD5 from 'spark-md5'

/**
 * 使用 spark-md5 生成文件MD5摘要
 * @resolve {string} md5
 */
export async function MD5(file) {
  return new Promise((resolve, reject) => {
    const blobSlice =
      File.prototype.slice ||
      File.prototype.mozSlice ||
      File.prototype.webkitSlice
    const chunkSize = 2097152 // Read in chunks of 2MB
    const chunks = Math.ceil(file.size / chunkSize)
    const spark = new SparkMD5.ArrayBuffer()
    const fileReader = new FileReader()
    let currentChunk = 0
    fileReader.onload = function(e) {
      spark.append(e.target.result) // Append array buffer
      currentChunk++
      if (currentChunk < chunks) {
        loadNext()
      } else {
        resolve(spark.end())
      }
    }
    fileReader.onerror = function(e) {
      reject(e)
    }
    function loadNext() {
      const start = currentChunk * chunkSize
      const end = start + chunkSize >= file.size ? file.size : start + chunkSize
      fileReader.readAsArrayBuffer(blobSlice.call(file, start, end))
    }
    loadNext()
  })
}