Plupload file upload md5

  // file md5 method
  function calculate(file, callBack) {
      let fileReader = new FileReader(),
        blobSlice = File.prototype.mozSlice || File.prototype.webkitSlice || File.prototype.slice,
        chunkSize = 2097152,
        // read in chunks of 2MB
        chunks = Math.ceil(file.size / chunkSize),
        currentChunk = 0,
        spark = new SparkMD5();

      fileReader.onload = function (e) {
        spark.appendBinary(e.target.result); // append binary string
        currentChunk++;

        if (currentChunk < chunks) {
          loadNext();
        }
        else {
          callBack(spark.end());
        }
      };

      function loadNext() {
        let start = currentChunk * chunkSize,
          end = start + chunkSize >= file.size ? file.size : start + chunkSize;

        fileReader.readAsBinaryString(blobSlice.call(file, start, end));
      };

      loadNext();
  }


// 文件上传回调
  function uploadCallback(status, remote_path, filename, callback_params, file){
        // 调用计算md5的方法
        calculate(file.getNative(), function (md5) {
            console.log(md5); //hash值
        });
       // other code ....
       // ....
 });