vue 上传图片限制大小和格式

<div class="upload-box clear"><span class="fl">上传图片</span><div class="artistDet-logo-box fl"><el-upload :action="this.baseServerUrl+'/fileUpload/uploadPic?filepath=artwork'" list-type="picture-card" :class="{disabled:uploadMainDisabled}"
　　　　　:file-list="imagelist" :on-preview="handlePictureMainPreview" :on-remove="handleMainRemove" :on-success="handleMainSuccess" :beforeUpload="beforeAvatarUpload">
      </el-upload><el-dialog :visible.sync="dialogMainVisible" ><img width="100%" :src="dialogMainImageUrl" alt=""></el-dialog></div>
</div>

beforeAvatarUpload(file) {                var testmsg=file.name.substring(file.name.lastIndexOf('.')+1)                 const extension = testmsg === 'jpg'  const extension2 = testmsg === 'png'  const isLt2M = file.size / 1024 / 1024 < 10  if(!extension && !extension2) {  this.$message({  message: '上传文件只能是 jpg、png格式!',  type: 'warning'  });  }  if(!isLt2M) {  this.$message({  message: '上传文件大小不能超过 10MB!',  type: 'warning'  });  }  return extension || extension2 && isLt2M  
} ,

将beforeAvatarUpload加到methods里面