el-upload file转blob 用于预览pdf.js和下载文件

   // file转blob
    fileToBlob(file, callback) {
      const type = file.type;
      const reader = new FileReader();
      reader.onload = (evt) => {
        const blob = new Blob([evt.target.result], { type });
        if (typeof callback === "function") {
          callback(blob);
        } else {
          console.log("我是 blob:", blob);
        }
      };
      reader.readAsDataURL(file);
    },
 
    analyzeZip(file) {
      const _file = file.raw;
      this.fileToBlob(_file, async (blob) => {
        console.log(blob);
      
      });