base64 转 blob 或 file 格式

// 转 file
　　dataURIToFile(dataURI) {
      let binStr = atob(dataURI.split(',')[1])
      let len = binStr.length
      let arr = new Uint8Array(len)

      for (var i = 0; i < len; i++) {
        arr[i] = binStr.charCodeAt(i);
      }
　　　　return new File([arr], `xx.pdf`, {
        type: 'application/pdf',
        lastModified: new Date()
      })
    }

// 转 blob

dataURIToBolb(dataURI) {
      let binStr = atob(dataURI.split(',')[1])
      let len = binStr.length
      let arr = new Uint8Array(len)

      for (var i = 0; i < len; i++) {
        arr[i] = binStr.charCodeAt(i);
      }
      return new Blob([arr], {
        type: 'application/pdf',
      })
    }