话不多说，直接上代码

<template>
  <el-dialog
    :title="!dataForm.id ? '新增' : '修改'"
    :close-on-click-modal="false"
    :visible.sync="visible">
    <el-form :model="dataForm" :rules="dataRule" ref="dataForm" @keyup.enter.native="dataFormSubmit()" label-width="80px">
      <el-form-item label="标题" prop="title">
        <el-input v-model="dataForm.title" placeholder="标题"></el-input>
      </el-form-item>
      <el-form-item label="附件" prop="files">
        <el-upload
          class="upload-demo"
          action
          :http-request="uploadFile"
          :before-upload="beforeUpload"
          name="file"
          :headers="headers"
          :data="uploadData"
          :file-list="fileList"
          :on-remove="removeFile"
          multiple>
          <el-button size="small" type="primary">点击上传</el-button>
          <div slot="tip" class="el-upload__tip">只能上传小于5M的文件</div>
        </el-upload>
      </el-form-item>
    </el-form>
    <span slot="footer" class="dialog-footer">
      <el-button @click="visible = false">取消</el-button>
      <el-button type="primary" @click="dataFormSubmit()">确定</el-button>
    </span>
  </el-dialog>
</template>

<script>
  export default {
    data () {
      return {
        visible: false,
        dataForm: {
          id: 0,
          title: ''
        },
        dataRule: {
        },
        uploadUrl: '',
        uploadData: {},
        fileList:[],
        headers: { "Content-Type": "multipart/form-data" },  //设置表头
        file: [],
        fileType: [ "pdf", "doc", "docx", "xls", "xlsx","txt","png","jpg", "bmp", "jpeg"],
      }
    },
    methods: {
      init (id) {
        this.dataForm.id = id || 0
        this.visible = true
        this.$nextTick(() => {
          this.$refs['dataForm'].resetFields()
          if (this.dataForm.id) {
            this.$http({
              url: this.$http.adornUrl(`/sys/sysnotify/info/${this.dataForm.id}`),
              method: 'get',
              params: this.$http.adornParams()
            }).then(({data}) => {
              if (data && data.code === 0) {
                this.dataForm.title = data.sysNotify.title
                //文件回显
                for (var i in data.fileList) {
                  //[{name: 'food.jpeg', url: 'https://fuss10.elemecdn.com/3/63/4e7f3a15429bfda99bce42a18cdd1jpeg.jpeg?imageMogr2/thumbnail/360x360/format/webp/quality/100'}]
                  this.fileList.push(data.fileList[i])
                }
              }
            })
          }
        })
      },
      // 表单提交
      dataFormSubmit () {
        this.$refs['dataForm'].validate((valid) => {
          if (valid) {
            //新建FormData上传
            let FormDatas = new FormData()
            //多文件上传
            for (var i in this.file) {
              FormDatas.append('file', this.file[i]);
            }
            FormDatas.append("id", this.dataForm.id || '');
            FormDatas.append("title", this.dataForm.title);

            this.$http({
              url: this.$http.adornUrl(`/sys/sysnotify/${!this.dataForm.id ? 'save' : 'update'}`),
              method: 'post',
              headers: this.headers,
              data: FormDatas
            }).then(({data}) => {
              if (data && data.code === 0) {
                this.$message({
                  message: '操作成功',
                  type: 'success',
                  duration: 1500,
                  onClose: () => {
                    this.visible = false
                    this.$emit('refreshDataList')
                  }
                })
              } else {
                this.$message.error(data.msg)
              }
            })
          }
        })
      },
      //上传文件之前验证文件类型和大小
      beforeUpload(file) {
        if (file.type != "" || file.type != null || file.type != undefined){
          //截取文件的后缀，判断文件类型
          const FileExt = file.name.replace(/.+\./, "").toLowerCase();
          //计算文件的大小
          const isLt5M = file.size / 1024 / 1024 < 5; //这里做文件大小限制
          //如果大于5M
          if (!isLt5M) {
            this.$message({
              message: '上传文件大小不能超过 5MB!',
              type: 'info'
            });
            return false;
          }
          //如果文件类型不在允许上传的范围内
          if(this.fileType.includes(FileExt)){
            return true;
          }
          else {
            this.$message.error("上传文件格式不正确!");
            return false;
          }
        }
      },

      //把上传文件放入列表中
      uploadFile(item){
        this.file.push(item.file)
      },

      //移除文件
      removeFile(item) {
        for (var i in this.file) {
          if (item.name == this.file[i].name) {
            this.file.splice(i, 1)
          }
        }
      }
    }
  }
</script>

《难经》