限制大小：

              <el-upload
                ref="upload"
                :limit="1"
                :action="imgAction"
                :show-file-list="false"
                :http-request="modeUpload"
                accept=".pdf"
                :on-change="handleChange"
                :file-list="fileList"
              >
                <el-button size="mini" type="primary">选择文件</el-button>
              </el-upload>

    modeUpload(item) {
      if (this.$refs.upload) {
        this.$refs.upload.clearFiles() // 清除上传的文件
      }
      this.upDateFileDialogData.uploadFileName = '' // 清除输入框文字
      this.fileItem = '' // 清除文件列表数组
      const file = item.file
      const size = file.size / 1024 / 1024
      if (size > 50) {
        this.$notify.warning({
          title: '警告',
          message: '大小必须小于50M'
        })
        return
      }
      this.fileItem = item.file // 获取要上传的文件
      this.upDateFileDialogData.uploadFileName = item.file.name // 给输入框赋值
      console.info('modeUploadfile', item.file.name)
    },

限制类型：

比如限制只能上传.pdf和.txt文件，则写法：

 <el-upload
	ref="upload"
	accept=".pdf, .txt"
 </el-upload>