导出CSV文件excel打开中文乱码，需增加BOM头

导出CSV文件，因没有BOM头，而导致 文本打开CSV文件时正常，excel打开是中文乱码。 解决办法是添加BOM头。 前端添加BOM头的示例方法如下：

async exportData() {
  let confirm = await this.$confirm(
    '默认导出【已归档】和【未归档】的患者数据，也可按照归档状态选择，是否继续？',
    '导出提示',
    {
      type: 'warning'
    }
  ).catch(action => {
    return false
  })
  if (confirm) {
    let dateStr = XEUtils.toDateString(new Date(), 'yyyyMMddhhmmss')
    let fileName = `data_${dateStr}.csv`
    let params = {
      orgcode: this.currentUserInfo.orgCodg,
      ...this.filter
    }
    const response = await firstPageService.exportData(params)
    // 处理文件下载
    // const blob = new Blob([response.data], {
    //   type: 'text/csv;charset=UTF-8'
    // })
    const BOM = new Uint8Array([0xEF, 0xBB, 0xBF])
    const arrayBuffer = await response.data.arrayBuffer()
    const combined = new Uint8Array(BOM.length + arrayBuffer.byteLength)
    combined.set(BOM, 0)
    combined.set(new Uint8Array(arrayBuffer), BOM.length)
    const blob = new Blob([combined], {
      type: 'text/csv;charset=UTF-8'
    })
    const downloadUrl = window.URL.createObjectURL(blob)
    const link = document.createElement('a')

    link.href = downloadUrl
    link.setAttribute('download', fileName)
    document.body.appendChild(link)
    link.click()

    // 清理资源
    window.URL.revokeObjectURL(downloadUrl)
    document.body.removeChild(link)

    this.$message({
      message: '导出成功',
      showClose: true,
      type: 'success'
    })
  }
},

关键部分是：

const BOM = new Uint8Array([0xEF, 0xBB, 0xBF])
const arrayBuffer = await response.data.arrayBuffer()
const combined = new Uint8Array(BOM.length + arrayBuffer.byteLength)
combined.set(BOM, 0)
combined.set(new Uint8Array(arrayBuffer), BOM.length)
const blob = new Blob([combined], {
  type: 'text/csv;charset=UTF-8'
})