el-upload使用beforeUpload不生效

    解决方式如下:

将auto-upload设置成false,用on-change来操作
<el-upload

              class="upload-demo"

              :action="uploadUrl"

              :auto-upload="false"

              :on-preview="handlePreview"

              :on-remove="handleRemove"

              :before-remove="beforeRemove"

              :on-success="handleSuccess"

              :on-exceed="handleExceed"

              :on-change="handleChange"

              :file-list="fileList"

              :limit="1"

            >

async handleChange (file, fileList){

      if (file.size / 1024 / 1024 > 5) {

        this.fileList = [];  //将列表清空

        this.$message.warning("上传文件大小不能超过 5MB!");

        return false;

      }

      this.fileList = fileList;
     // 传参用的是FormData类型

      let formData = new FormData();

      formData.append('file',file.raw); //file类型是binary

      formData.append('fileName', file.name);

      const res = await infoApi.uploadFile(formData);

    },