vue el-upload 上传文件格式校验方法

<el-upload
  class="avatar-uploader"
  action="#"
  :show-file-list="false"
  :before-upload="beforeAvatarUpload">
  <i class="el-icon-plus avatar-uploader-icon"></i>
</el-upload>

<script>
  export default {
    methods: {
      beforeAvatarUpload(file) {
        const isLt2M = file.size / 1024 / 1024 < 2;  // 小于2M
        if ( !isLt2M ) {
            console.log('文件大小超出2M');
        }
      }
    }
  }
</script>

file.name.split('.')[1].toLowerCase() != 'mp4'; // 视频不是.mp4格式的

let formatArr = ['image/png','image/jpg','image/jpeg'];
const isPic = ( formatArr.indexOf(file.type.toLowerCase()) != -1 );  // 是否为图片

// 获取视频文件时长
getVideoTime(file){
    return new Promise((resolve, reject) => {
        let url = URL.createObjectURL(file);
        let audioElement = new Audio(url);
        audioElement.addEventListener('loadedmetadata',function(_event){
            const time = Math.round(audioElement.duration * 100) / 100;   // 时长为秒，保留两位小数
            resolve(time);
        });
        audioElement.addEventListener('error', () => resolve(0));
    })
},

 data(){
      return {
        ...
        //判断是否需要做文件检查
        checkFileFormat:false
      }
    },
    beforeUpload(rawFile) {
      this.loading = true;
      ...
      检查文件格式
      检查文件大小
      ...
      if (this.checkFileFormat) {
        return new Promise(async (resolve, reject) => {
          const fd = new FormData()
          fd.append('file', rawFile)
          const res = await checkRpAttFile(fd)
          this.loading = false;
          if (!res.success) {
            Message.error(res.message);
            reject()
          } else {
            resolve()
          }
        })
      } else {
        return true
      }
    },