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