js 上传文件进行base64转换,且只能上传csv文件

html

<el-upload
  class="base"
   ref="upload"
   action=""
   accept=".csv"
   :before-upload="beforeFileUpload"
   :on-change="handleFileUploaderChange"
   :auto-upload="false"
   :show-file-list="false"
  >
   <el-button
     class="base"
     size="small"
     type="primary"
     >上传文件</el-button>
</el-upload>

方法

    handleFileUploaderChange (file) {
      let testmsg = file.name.substring(file.name.lastIndexOf('.') + 1)
      if (testmsg !== 'csv') {
        this.$message.error(this.$t('certifivateNo.formatError'))
        return
      }
      let reader = new FileReader()
      if (file) {
        reader.readAsDataURL(file.raw)
      }
      reader.onload = () => {
       //执行的方法
      }
    }