关于vue加element-ui上传文件获取文件的sha256的值

首先使用element的上传文件的组件

安装依赖crypto-js

npm i crypto-js

　　　　　　　<el-upload
              class="upload-demo"
              drag
              :http-request="uploadCrt"
              action=""
              :limit='1'
              :file-list="fileList"
              :on-exceed='_change'

            >
              <i class="el-icon-upload"></i>
              <div class="el-upload__text">
                将文件拖到此处，或<em>点击上传</em>
              </div>
            </el-upload>

然后写方法

  uploadCrt(param) {

      let that = this;
      var contractFile = param.file;
      // console.log(contractFile)
      var reader = new FileReader(),
        self = this;
      var blobSlice =
        File.prototype.mozSlice ||
        File.prototype.webkitSlice ||
        File.prototype.slice;
      var chunkSize = 6 * 1024 * 1024;
      var chunks = Math.ceil(contractFile.size / chunkSize);
      var currentChunk = 0;
      var hasher = CryptoJS.algo.SHA256.create();
      var start = currentChunk * chunkSize;
      var end =
        start + chunkSize >= contractFile.size
          ? contractFile.size
          : start + chunkSize;
      reader.readAsArrayBuffer(blobSlice.call(contractFile, start, end));
      reader.onload = function (evt) {
        var fileStr = evt.target.result;
        var tmpWordArray = self.arrayBufferToWordArray(fileStr);
        hasher.update(tmpWordArray);
        currentChunk += 1;
        fileStr = null;
        tmpWordArray = null;
        if (currentChunk < chunks) {
          var start = currentChunk * chunkSize;
          var end =
            start + chunkSize >= contractFile.size
              ? contractFile.size
              : start + chunkSize;
          reader.readAsArrayBuffer(blobSlice.call(contractFile, start, end));
        }
      };
      reader.onloadend = function () {
        contractFile = null;
        var hash = hasher.finalize();
        hash.toString(); //计算结果
        that.filehash = hash.toString();
        console.log(that.filehash)
        hasher = null;
        blobSlice = null;
        reader = null;
        hash = null;
      };
    },
    arrayBufferToWordArray(ab) {
      var i8a = new Uint8Array(ab);
      var a = [];
      for (var i = 0; i < i8a.length; i += 4) {
        a.push(
          (i8a[i] << 24) | (i8a[i + 1] << 16) | (i8a[i + 2] << 8) | i8a[i + 3]
        );
      }
      return CryptoJS.lib.WordArray.create(a, i8a.length);
    },

　　计算结果sha256的值